Though Leon Ruff made a couple of appearances in NXT from 2019-2020, he wasn't actually signed to WWE until October 2020. He then officially joined the NXT brand and wasted no time in making his mark, as he won the North American Championship just one month after signing.

Ruff defeated Johnny Gargano for the title, and he recalled when NXT head coach Matt Bloom told him he was going to become the champion when interviewed on Instinct Culture.

"That moment, everything that I did to pursue wrestling, every sacrifice that I made was worth it. I felt validated. It felt good to know that it paid off; I did myself a good job. I was doing a lot of work and I just kept telling myself, 'If you keep doing this, one day, it will all pay off.' So when it all did, it was a great moment... I couldn't believe it because, at first, I thought it was a joke," Ruff said of Bloom telling him.

"I thought somebody was playing a prank on the new guy, 'Yo, we're gonna make him believe this and then we're gonna see how he looks when we tell him no.' But when I found out it was real, I had to take a second to think because Johnny Gargano is somebody that I admire a lot. When I discovered who he was on the independent scene, I started to watch a lot of his matches and his documentaries. I used to write a lot of notes about him. So not only to wrestle him on TV but to take the title from him? It was mind blowing. I couldn't believe I got the opportunity to do it, and I felt really fortunate."

As part of his early appearances with WWE, Ruff had a pair of matches with Aleister Black in March 2020. The first was for a Main Event taping, and the two did so well that the following week they had another match on Raw. Ruff credits those matches as being what spurred WWE to bring him in full-time.

"I can honestly say it was the Aleister Black match because we ended up having a match twice. I see a lot of wrestlers that will come and just go through the motions and get it over with because they're not shining, they're not the stars. But I feel that, with me, they saw somebody who was willing to take the extra step, go the extra mile. No matter how much time he's given, he'll make the most of it. I felt like that's what they saw, somebody who makes the most out of a little," stated Ruff.

Since winning the North American Championship, Ruff has defended it just once in a rematch against Gargano. He talked about the other NXT Superstars he's looking to put the title on the line against.

"As champion, I would love to face Timothy Thatcher, I would love to face Adam Cole, I would love to face Tommaso Ciampa again, he's just a great guy," said Ruff. "Cameron Grimes and Dexter Lumis; love, love to work with Dexter Lumis."