In August 2021, Brutus and his brother Julius Creed appeared on WWE NXT as members of Roderick Strong's Diamond Mine stable. They made their in-ring debut at the August 24, 2021 WWE NXT tapings (with their match airing on September 7, 2021), defeating Chuckie Viola and Paxton Averill in a squash.
On February 15, 2022, at NXT Vengeance Day, The Creed Brothers defeated MSK to win the men's Dusty Rhodes Tag Team Classic. On June 4, at NXT In Your House, they defeated Pretty Deadly to win the NXT Tag Team Championship. At Worlds Collide on September 4, The Creed Brothers lost the NXT Tag Team Championships to Pretty Deadly in a fatal-four way elimination tag team title unification match, involving the NXT UK Tag Team Champions Josh Briggs and Brooks Jensen, and Gallus (Mark Coffey and Wolfgang), after Damon Kemp turned on Diamond Mine by hitting Julius Creed with a steel chair, ending their reign at 92 days. The Creeds would fail to win the tag titles in a steel cage one week later due to interference from Kemp. This led to a match at NXT Halloween Havoc, where Julius defeated Kemp. The Creeds would fail to win the NXT Tag Team Championships throughout 2023. At NXT Stand and Deliver, the Creeds failed to in the tag titles from Gallus in a triple threat tag team match, and on the April 18 episode of NXT in another triple threat involving the The Dyad at NXT Battleground. On the July 4 episode of NXT, the Creed Brothers lost to the Dyad in a "Loser Leaves NXT" tag team match. They were reinstated the following month after defeating the Dyad in a cage match.
The Creed Brothers, along with fellow Diamond Mine member Ivy Nile, made their main roster debut on the October 30 episode of Raw, defeating Alpha Academy. At Halloween Havoc the following day, they defeated Angel Garza and Humberto Carrillo in a "Tables, Ladders, and Scares match" in their final match for NXT. On the November 6 episode of Raw, the Creed Brothers (and Ivy Nile) formally joined the Raw brand. On the November 27 episode of Raw, the Creed Brothers won a tag team turmoil match for an Undisputed WWE Tag Team Championship opportunity; however, they failed to defeat the Judgment Day for the titles on the December 18 episode of Raw.