But it wasn't the first time Lesnar exited the Octagon uneasy. The former champion had never felt comfortable letting his hands go in stand-up.
Although most observers believe Lesnar (5-2-0) lacks stand-up skills, he's quick to dismiss that notion. He claims to have good punching abilities, at least in the gym.
The problem occurs inside the Octagon. Going into his title bout at UFC 121, Lesnar was not yet comfortable letting his hands go on fight night.
He's comfortable now, he says. And he credits the Velasquez fight with getting him over the hump.
"I stood there and traded with Velasquez, and in this game, in the heavyweight division, it's a matter of inches," Lesnar told ESPN.com. "I got him uncomfortable enough to make him shoot in on me.
"Going back and looking at the fight, it was toe-to-toe. We were toe-to-toe in all aspects of the stand-up. When I stood back up in the transition was when I got caught with a left uppercut and wasn't able to recover.
"After watching the fight, I came out of my evaluation with confidence. I just have to step in there and execute."
With his comfort level inside the Octagon and stand-up confidence on the rise, Lesnar is eager to step into the cage with his next opponent, Junior dos Santos.
They are scheduled to meet June 11 at UFC 131 in Vancouver, British Columbia. The winner gets a shot at Velasquez for the title.
"He'd better get good with his double-leg takedown defense," Lesnar said of dos Santos. "There hasn't been a heavyweight that I've faced who I haven't been able to take down.
"That's a helluva lot harder to learn than what I have to learn.
"I can take this fight wherever I want to take it. And that's half the battle right there."
Before stepping into the cage, Lesnar and dos Santos will coach opposite one another on "The Ultimate Fighter" Season 13 series. The series is scheduled to debut on Wednesday (Spike TV at 9 p.m. ET).
It was on the set of TUF that dos Santos (12-1-0) got an opportunity to see the new, more comfortable and confident Lesnar. He was impressed.
"I didn't know Brock before," dos Santos said during a recent conference call to promote TUF 13. "But after getting to know him on the show, Brock is a professional guy. He's a pretty nice guy.
"But on June 11, none of that really matters. My goal is to go in there and beat Brock."
Franklin McNeil covers MMA and boxing for ESPN.com. He also appears regularly on "MMA Live," which airs on ESPN2. Follow him on Twitter at http://twitter.com/Franklin_McNeil.