Cain Velasquez needed just over four minutes at UFC 121 to accomplish what no fighter has done before: stop defending UFC heavyweight champion Brock Lesnar with strikes.

Velasquez's TKO of the champ came near the end of a round that featured frenetic action from both fighters. 

Lesnar came out hard from the start in a clear attempt to overwhelm his smaller opponent, but in Velasquez he at last had found a man who could match his athleticism, if not his size. Although Lesnar briefly managed to take Velasquez to the ground and gain top position, Velasquez was quickly able to regain his feet, and from that moment on the fight was his.

Lesnar continued to fight back gamely against the younger, faster Velasquez, but once he was back up pressing the attack the outcome never really seemed to be in doubt. Velasquez's impresive cardio was on full display as he relentlessly took the fight to the champ, landing repeated heavy strikes that eventually dropped Lesnar to the mat.

Once the fight hit the ground for the last time Lesnar did his best to escape damage and survive to the bell. It was a scene that was strangely reminiscent of his last fight, which saw the first round end with the champ on the ground surviving a savage beating from challenger Shane Carwin. In that fight, of course, Lesnar was able to submit an exhausted, punched out Carwin early in the second round.

Velasquez was not about to let the belt slip away in the same way.

Even the toughest fighters can only take so much punishment, and as Velasquez continued to land dangerous punches to his bloodied opponent referee Herb Dean finally had no choice but to step in and stop the fight.

Lesnar, his bearded face a mass of contusions, was gracious in defeat.

"He's a great fighter," said the former champ. "Congratulations, Cain. What can I say? He was better than me tonight."

For his part, Velasquez confided that he had been a little surprised at the early ferocity of Lesnar's assault.

"We knew his game plan going in, and it kind of surprised me how hard he did go for it in the beginning," Velasquez said. "I kind of froze just a little bit. I wasn't as relaxed as I should have been, but I think after that takedown he got on me, that's when I was like, 'OK, relax.'"

Once Velasquez had Lesnar down at the end of the fight, he says he knew he had to be deliberate with his attack.

"I knew the ref wasn't going to stop it that early," Velasquez said. "So we had to pick our shots. I wasn't just going to go crazy (with) punches if he was on bottom. He was covering up well. I wanted some punches to connect, and some elbows to get in there, so I took my time and really thought about where I should throw the punches and where I should give the elbows."

In the end, Velasquez believes that what made the difference against his larger opponent was his training.

"I felt his strength, and I felt his power, and I was definitely used to competing with guys that were just as strong as him," Velasquez stated. "I just think I was well-prepared for this fight."

Velasquez (9-0) is expected to face top challenger Junior Dos Santos (12-1) at an undetermined date for his first title defense.

Make sure to check back with us the day of the event for free, live, round-by-round coverage of UFC 121 right here at FiveKnuckles.com! Join expert analyst Mike Williams as he takes you through the entire fight card blow-by-blow and then keep it right here for all the post-fight news and notes you can handle!