Alex Shelley, whose real name is Patrick Kenneth Martin, began training in early 2002 under Breyer Wellington and Truth Martini. He then joined Border City Wrestling's Can-Am Wrestling School, training under Joe E. Legend and Scott D'Amore.

Six months into his career, Shelley was hospitalized with a shattered jaw after slipping on a wet ring and hitting the unpadded ring apron. He had steel plates inserted into his jaw as a result.

Martin debuted as Alex Shelley in March 2002. He created the name by combining the forename of Alex, the protagonist of the 1962 novel A Clockwork Orange, with the surname of Pete Shelley, the lead singer of the 1970s punk rock band the Buzzcocks.

After eight months, Shelley joined Ian Rotten's IWA Mid-South promotion. He worked there for six months before joining Combat Zone Wrestling in Philadelphia, and then Ring of Honor (ROH).

Shelley debuted in Ring of Honor at WrestleRave 2003, facing B. J. Whitmer, Tony Mamaluke and Jimmy Jacobs in a Four Corners Survival match, which was won by Whitmer.

Shelley requested his release from TNA late that year after booker Dusty Rhodes stopped utilizing him.

At Generation Next, Shelley formed a stable, "Generation Next", with Austin Aries, Jack Evans and Roderick Strong. Generation Next spent the entirety of the event attacking other wrestlers, claiming that they were "the best that Ring of Honor has to offer".

Shelley signed a non–exclusive contract with Total Nonstop Action Wrestling.

Shelley lost to Doug Williams in the finals of a tournament for the vacant ROH Pure Championship. That same night, Generation Next attacked Ricky Steamboat during his confrontation with CM Punk, with Punk subsequently siding with Steamboat to fend off Generation Next.

Generation Next faced CM Punk, John Walters, Jimmy Jacobs and Ace Steel in an eight–man elimination match at The Midnight Express Reunion. Generation Next won the match, with Shelley and Aries surviving. Following the match, Shelley announced his intention of challenging Samoa Joe for the ROH World Championship.

At Final Battle 2004, Shelley and Strong were defeated by CM Punk and Steve Corino. Following the match, Aries, feeling that Shelley was spending far too much time in Total Nonstop Action Wrestling (TNA) than he was leading Generation Next, demanded that Shelley step–down as the leader. Before Shelley could give an answer, he was attacked by Aries and Strong and kicked out of Generation Next.

Shelley signed a new contract with TNA after Rhodes resigned as TNA booker, and returned at Slammiversary, losing to Shocker.

Shelley joined Pro Wrestling Zero1-Max.

Shelley unsuccessfully challenged Aries for the ROH World Championship at Manhattan Mayhem.

Shelley returned to TNA at Slammiversary, losing to Shocker.

Shelley formed a tag team with Michael Shane, with the duo losing to America's Most Wanted at No Surrender 2005.

Shelley revealed that he had joined "The Embassy", a heel stable controlled by Prince Nana. Teaming with Fast Eddie Vegas that night, The Embassy won their first match in a feud with Generation Next that would last for the remainder of the year.

Shelley entered the TNA 2005 Super X Cup Tournament, but lost to Samoa Joe in the semifinals.

Shelley entered the Chris Candido Memorial Tag Team Tournament with Sean Waltman as his tag team partner, and won the tournament by defeating Shocker and Chris Sabin in the finals.

Shelley won the vacant Zero1-Max United States Openweight Championship, defeating Sonjay Dutt.

Austin Aries, Roderick Strong, Jack Evans and Matt Sydal of Generation Next defeated Shelley, Jimmy Rave, Abyss and Nana of The Embassy in an eight–man elimination steel cage match.

The Embassy of Shelley, Rave and Abyss won the 2006 Trios Tournament defeating Generation Next of Jack Evans and Matt Sydal and their partner Jimmy Yang in the finals, and thus each wrestler was granted any match they wanted, with Shelley and Rave both announcing they wanted a shot at the ROH World Championship.

Shelley got his title shot at Arena Warfare, but was unable to defeat Danielson.

Shelley teamed up with Rave to defeat the duo of Claudio Castagnoli and Azrieal.

Shelley was originally scheduled to face Danielson for the ROH World title, but a severe snowstorm hit the Northeast and Shelley was told by Total Nonstop Action Wrestling to fly back early to Orlando, Florida, so he would not miss their pay-per-view the following day.

Shelley's last appearance as a regular in Ring of Honor took place when he managed Jimmy Rave and Conrad Kennedy III in a losing effort against the Briscoe Brothers.

Shelley teamed with Kevin Nash to face Chris Sabin and Jay Lethal in a losing effort.

Shelley and Chris Sabin became NWA International Lightweight Tag Team Champions, when they defeated champions, Ikuto Hidaka and Minoru Fujita.

Shelley appeared in Kevin Nash's Open Invitational X Division Battle Royal at Bound for Glory. He lost the match to Austin Starr.

Shelley helped LAX win the match by hitting Brother Devon with a video camera and giving him a Frog Splash through a table.

Shelley lost in the five–man Xscape match at Lockdown 2007. He was pinned by Jay Lethal.

Shelley began wrestling as a tag team in TNA with Chris Sabin. The two had been teaming in several independent promotions under the names Murder City Machine Guns and The Motor City Machine Guns.

Shelley and Chris Sabin returned to ROH following the Briscoe Brothers winning the ROH World Tag Team Championship. The two challenged Jay Briscoe for a shot at the title on April 28 in Chicago, then attacked him after he accepted. The two would ultimately lose the match and leave the company.

Shelley and Sabin along with Jay Lethal were able to defeat Team 3D and Johnny Devine in a Street Fight at Against All Odds to save the X Division and to end the feud. With the win, Team 3D were forced to drop their weights under 275 pounds if they wanted to keep on wrestling for the company.

Shelley, Sabin and Curry Man represented Team TNA in the twelve–man, four–team elimination tag team match. Shelley made it to the end of the match and finally pinned Masato Yoshino of Team Japan to win the match and give Team TNA the lead ahead of the final round of the tournament.

Shelley and Chris Sabin lost the NWA International Lightweight Tag Team titles to the team of Minoru Fujita and Takuya Sugawara.

Shelley and Sabin defeated Daivari and Tyson Dux of Team International to give Team TNA their first point.

Shelley and five other TNA wrestlers traveled to Mexico to compete in the Consejo Mundial de Lucha Libre International Grand Prix, contested in a sixteen–man torneo cibernetico match. In the end, Shelley managed to avenge Team TNA's loss in the World X Cup, by winning the Gran Prix, after pinning Último Guerrero.

Shelley, Sabin and Sonjay Dutt unsuccessfully challenged Guerrero, Atlantis and Negro Casas for the CMLL World Trios Championship.

Shelley, Samoa Joe, A.J. Styles, Jay Lethal, Consequences Creed, Petey Williams, Eric Young, ODB and Chris Sabin formed a faction knows as The Frontline to battle The Main Event Mafia of Kurt Angle, Sting, Kevin Nash, Booker T and Scott Steiner.

Shelley took part in the second annual Turkey Bowl, defeating Cute Kip and Consequences Creed in a three–way dance in the semifinals. In the finals Shelley faced the reigning X Division Champion Sheik Abdul Bashir and Rhino in another three–way dance where the winner would receive a check for $25,000, and the loser had to wear a turkey suit. Rhino won the match, pinning Shelley following a Gore forcing him to wear the suit.

Shelley and Sabin competed in the Feast or Fired match, but did not win a title contract.

Shelley qualified for the finals in the X Division title tournament after defeating Jay Lethal and Eric Young.

Shelley defeated his tag team partner Chris Sabin for his first reign as the X Division Champion.

Shelley, Sabin, Lethal, Creed and Suicide competed in the first ever X Division Title King of the Mountain match, in which Shelley was unsuccessful in regaining the title.

Shelley and Sabin defeated No Limit (Tetsuya Naito and Yujiro) at New Japan Pro-Wrestling's Wrestle Kingdom III in Tokyo Dome to win the IWGP Junior Heavyweight Tag Team Championship.

Shelley lost the X Division Championship to Suicide in an Ultimate X match, which included Jay Lethal, Consequences Creed, and Chris Sabin.

Shelley and Sabin lost the IWGP Junior Heavyweight Tag Team Title to Apollo 55 (Prince Devitt and Ryusuke Taguchi).

Shelley and Sabin defeated Generation Me (Jeremy Buck and Max Buck) in an Ultimate X match to earn another shot at the TNA World Tag Team Championship.

The Motor City Machine Guns defeated Beer Money, Inc. and Team 3D in a three–way match to earn another shot at the Tag Team Championship.

The Motor City Machine Guns defeated Generation Me to retain the TNA World Tag Team Championship.

Ring of Honor announced at their 8th Anniversary Show that the Motor City Machine Guns would return to the company on May 8 in New York City.

Shelley and Sabin received their title shot on the April 12 Impact!, but were defeated by World Tag Team Champion Matt Morgan and Amazing Red, who replaced the injured Hernandez in the match.

The Motor City Machine Guns were defeated by the ROH World Tag Team Champions The Kings of Wrestling (Chris Hero and Claudio Castagnoli) via disqualification, when the Briscoe Brothers interfered in the match.

The Motor City Machine Guns defeated Beer Money, Inc. in a Two Out of Three Falls match to win the Best of Five Series and retain the TNA World Tag Team Championship.

Shelley defeated Amazing Red, Robbie E and Shannon Moore in an Ultimate X match to become the number one contender to the TNA X Division Championship.

Shelley broke his collarbone during a match in Hagerstown, Maryland.

Shelley made his return, saving Sabin from Mexican America (Anarquia and Hernandez).

Shelley and Storm were successful in their title defense.

Shelley received his shot at the X Division Championship, held by Brian Kendrick, but was defeated following outside interference from Austin Aries.

Shelley and Aries competed in a three-way match for the TNA X Division Championship, but were both unable to win the belt from the defending champion, Brian Kendrick.

Shelley and Kushida forming the tag team "Time Splitters".

Shelley confronted and challenged X Division Champion Austin Aries.

Shelley was unsuccessful in his title challenge against Aries, after submitting to the Last Chancery.

TNA started promoting the returns of Chris Sabin and the Motor City Machine Guns.

The Motor City Machine Guns unsuccessfully challenged Magnus and Joe for the TNA World Tag Team Championship in a steel cage match.

It was reported that Shelley had chosen not to renew his contract with TNA, ending his eight-year run with the promotion.

New Japan announced that Shelley would be returning to the promotion the following month.

Shelley and A.J. Kirsch unsuccessfully challenged Forever Hooligans (Alex Koslov and Rocky Romero) for the IWGP Junior Heavyweight Tag Team Championship.

Shelley wrestled his New Japan return match, when he, Bushi, Máscara Dorada and Ryusuke Taguchi were defeated in an eight-man tag team match by Alex Koslov, Averno, Low Ki and Rocky Romero.

Time Splitters unsuccessfully challenged Forever Hooligans for the IWGP Junior Heavyweight Tag Team Championship.

The Time Splitters entered the 2012 Super Jr. Tag Tournament, defeating Jado & Gedo in their first round match.

Time Splitters defeated Jyushin Thunder Liger and Tiger Mask.

Shelley took part in the 2013 Best of the Super Juniors, where he managed to win five out of his eight matches with a win over Ricochet in the final round-robin match of the tournament on June 6, earning him a spot in the semifinals.

Shelley was defeated in the finals of the tournament by Prince Devitt.

Shelley and Kushida defeated Suzuki-gun (Taichi and Taka Michinoku) to earn another shot at the Forever Hooligans and the IWGP Junior Heavyweight Tag Team Championship.

Shelley suffered a back injury, which would force Time Splitters to back out of the title match. Shelley later revealed that he had received a severe sciatica taking a sitout powerbomb from Taichi, which marked his fourth injury in the promotion since his September 2012 return.

Time Splitters received their title shot, but were again defeated by The Young Bucks.

Time Splitters received another title shot at Global Wars, a special event co-produced by NJPW and ROH in Toronto, but were defeated by The Young Bucks in a three-way match, also involving Forever Hooligans.

Shelley entered the 2014 Best of the Super Juniors tournament, where he won his block with a record of four wins and three losses, advancing to the semifinals. However, after injuring his left shoulder in his final round-robin match on June 6, Shelley was forced to pull out of the semifinals.

Shelley and Kushida defeated The Young Bucks to win the IWGP Junior Heavyweight Tag Team Championship for the second time as a team.

Time Splitters made their second successful title defense against Suzuki-gun (El Desperado and Taichi).

Shelley returned to ROH at Final Battle 2014, where he and Kushida unsuccessfully challenged reDRagon (Bobby Fish and Kyle O'Reilly) for the ROH World Tag Team Championship.

Time Splitters received a rematch for the IWGP Junior Heavyweight Tag Team Championship in a four-way match also involving Forever Hooligans and The Young Bucks, but were again defeated by reDRagon.

Shelley suffered ligament damage and an avulsion fracture in his left foot, which forced him to pull out of the 2015 Best of the Super Juniors.

Shelley unsuccessfully challenged Kenny Omega for the IWGP Junior Heavyweight Championship.

The Time Splitters returned to ROH, losing to the Briscoes at Field of Honor.

Shelley and Kushida unsuccessfully challenged reDRagon for the IWGP Junior Heavyweight Tag Team Championship.

Shelley teamed with A. C. H. and Matt Sydal to defeat Sabin, Daniels and Kazarian in a six-man tag team match.

Shelley and Sabin then formed a stable named "Search and Destroy" with Jay White, Jonathan Gresham and Lio Rush.

Sabin turned on Daniels and Kazarian, re-forming the Motor City Machine Guns with Shelley.

Shelley and Sabin defeated Daniels and Kazarian in their return match.

Shelley confirmed he had signed with ROH and would work for the promotion regularly going forward.

The Motor City Machine Guns unsuccessfully challenged The Addiction for the ROH World Tag Team Championship.

NJPW announced that Shelley would return to the promotion, now again as part of the Motor City Machine Guns tag team with Chris Sabin.

The Motor City Machine Guns unsuccessfully challenged The Young Bucks for the IWGP Junior Heavyweight Tag Team Championship.

The Motor City Machine Guns took part in a three-way ladder match for the ROH World Tag Team Championship, which was won by The Young Bucks (Matt Jackson and Nick Jackson) and also included The Addiction.

The Motor City Machine Guns lost the ROH World Tag Team Championship against The Briscoe Brothers.

It was reported Shelley's contract with ROH expired and left the promotion to focus on his wrestling school. Four days after, Shelley announced his kayfabe retirement; in reality, Shelley started his clinicals for physical therapy school and devoted his time to prepare for his post-in-ring career.

Shelley came out of retirement to team up with Jay Lethal and Jonathan Gresham to beat The Kingdom.

Shelley was defeated by Matt Taven for the ROH World Championship.

Shelley defeated Colt Cabana.

The Motor City Machine Guns defeated the North to capture the Impact World Tag Team Championship for a second time, ending their 383 days reign.

Shelley was coming to WWE, as part of the NXT brand and would be Kushida's partner, reforming their Time Splitters tag team for the first time since their New Japan Pro Wrestling days in 2015; this is Shelley's first time performing on WWE, after a one-off appearance on WWE Heat back in his early wrestling days in 2005.

Shelley and Kushida lost to Grizzled Young Veterans (James Drake and Zack Gibson) in the first round of the tournament.

Shelley made his return to TNA, now known as Impact Wrestling, alongside Chris Sabin as the Motor City Machine Guns defeating the Rascalz after answering their open challenge.

Shelley and Sabin defeated XXXL (Acey Romero and Larry D).

Shelley made his Pro Wrestling Guerrilla (PWG) debut, defeating Jonathan Gresham to become the number one contender for the PWG World Championship.

Shelley made his MLW debut at Fightland where he lost to TJP in the Opera Cup quarter-finals.

Shelley participated in the 2022 PWG Battle of Los Angeles. He defeated Lee Moriarty in the first round, but lost to Daniel Garcia in the second round.

Shelley returned to Impact Wrestling to face his student Jay White in a losing effort.

Shelley was defeated by Mike Bailey.

Shelley defeated Sabin in an Impact World Championship number one contender match.

Shelley unsuccessfully challenged Josh Alexander for the Impact World Championship.

Sonjay Dutt announced that Jay Lethal would team with the Motor City Machine Guns at the All Out PPV, where they would take on Wardlow and FTR in a six-man tag-team match, with Sabin and Shelley set to make their All Elite Wrestling (AEW) debut. At the event, Wardlow and FTR would win the match, with assistance from Samoa Joe, who attacked Satnam Singh early in the match.

Sabin and Shelley made their return to New Japan Pro-Wrestling at Rumble on 44th Street. At the event, the duo defeated Aussie Open to win the Strong Openweight Tag Team Championships, in a three-way match, also involving The DKC and Kevin Knight.

The Guns defeated Heath and Rhino to capture the Impact World Tag Team Championship for a third time, ending their 62 days reign.

Shelley defended the Impact World Championship against Alexander.

The Motor City Machine Guns lost their titles to Bullet Club members Ace Austin and Chris Bey, ending their reign at 78 days.

Shelley defeated Eddie Edwards, Frankie Kazarian, Jonathan Gresham, Moose and Yuya Uemura to become the number one contender for Impact World Championship at Against All Odds.

Shelley successfully defended his title against Nick Aldis.

Shelley defended his title against Brian Myers and against Hiroshi Tanahashi.

Shelley and Sabin were defeated by Alexander and Zack Sabre Jr. in a tag team match.

Shelley was unsuccessful at winning the TNA World Championship against Moose in a No Surrender Rules match.

Shelley alongside Sabin wrestled their final matches for TNA in a losing effort against The System (Eddie Edwards and Brian Myers), as their contracts expired on April 1, 2024.

It was reported that Shelley and Sabin signed with WWE, marking Shelley's return to the company after four years, with his last appearance being a one-off deal in 2020.

Shelley and Sabin made their debut on the SmackDown brand, winning the WWE Tag Team Championships next week after they defeated The Bloodline (Tonga Loa and Tama Tonga).