In June 2015, Slapjack took part in a WWE tryout camp. In February 2016, it was reported that he, under the ring name Shane Thorne, as well as tag team partner Nick Miller, were scheduled to join WWE's NXT brand.
On 25 March 2016, WWE confirmed the signings of both Thorne and Miller. They began training at the WWE Performance Center in April. They debuted as TM-61 on the 25 May episode, losing to Johnny Gargano and Tommaso Ciampa. On 19 November, at NXT TakeOver: Toronto, TM61 lost in the finals of the Dusty Rhodes Tag Team Classic to The Authors of Pain. Thorne then had knee surgery, which was expected to sideline him for seven to nine months. He returned on 14 September, 2017. TM-61 returned to NXT television on 31 January 2018, to face the Ealy Brothers in a winning effort. TM-61 then entered the 2018 Dusty Rhodes Tag Team Classic, being eliminated by The Authors of Pain in the first round. On the 1 May edition of NXT, TM-61 turned heel by defeating The Street Profits (Angelo Dawkins and Montez Ford) with a dirty pin. The following week they beat the team of Heavy Machinery (Otis Dozovic and Tucker Knight) with the same tactics. The team was officially renamed, "The Mighty", on the 6 June episode of NXT. On 14 December Miller was released from his WWE contract, disbanding The Mighty. On 22 January 2019, WWE announced that Thorne would be replacing Otis Dozovic in the Worlds Collide tournament. On 26 January 2019 (aired 2 February) Thorne was eliminated in the first round by Adam Cole. On the August 28, 2019 edition of NXT, Thorne lost to Bronson Reed. On the September 11 episode of NXT, Thorne had a confrontation with Johnny Gargano, who was speaking about his NXT future, this led to a match between the two, in which Thorne was defeated.
In March 2020, Thorne began appearing on Raw alongside Brendan Vink, where they lost to teams such as Street Profits and Cedric Alexander and Ricochet. On the April 27, 2020 episode of Raw, Thorne and Vink became MVP’s newest associates as he challenged Alexander and Ricochet to a match the next week on their behalf. The following week, Thorne and Vink defeated Alexander and Ricochet.
After a hiatus from television, on the September 21, 2020 episode of Raw, Thorne was officially revealed as one of the main members of the Retribution faction, under the new ring name Slapjack. At the Hell in a Cell event, Slapjack challenged Bobby Lashley for the United States Championship, but lost. Retribution disbanded on the Fastlane kickoff show, where Reckoning and Slapjack walked out on leader Mustafa Ali, then T-Bar and Mace performed a double chokeslam on Ali after he lost a match for the United States Championship to Riddle. On the April 9, 2021 episode of SmackDown, Slapjack took part in the André the Giant Memorial Battle Royal, but failed to win the match. Following this, Slapjack would be taken off television for several months.
After the July 16 episode of SmackDown, Slapjack returned under his original Shane Thorne name, in a dark match battle royal as a face. He would wrestle two more dark matches in September with a loss to Keith Lee and a win over Austin Theory respectively. On November 18, Thorne was released from his WWE contract without ever reappearing on television.