"I can't believe it," Lesnar (3-1) said after the win, echoing the sentiments of many who thought him simply too inexperienced to beat the veteran champion. "I may come off as a cocky S.O.B., but I just believe in hard work."
Lesnar relished his victory by climbing atop the Octagon and mugging for the crowd, but later gave Couture (16-9) credit for coming back after a year-long layoff and taking on "a young buck like me."
Despite showing some holes in his game, it was Lesnar's striking, and not his wrestling, that made the difference. A right hand from Lesnar landed just behind Couture's ear midway through the round, dropping him in a heap. Lesnar wasted no time in pouncing on the UFC hall of famer and finishing him with a torrent of unanswered hammer fists 3:07 into the second round.
"Those were some big ham hocks coming at me," said a battered, but good-humored Couture. "It's hard to get out of the way. He's a big guy and he caught me with a big shot."
The 45-year-old former champion appeared to have the edge in the striking department in the second round after being overpowered both in the clinch and on the mat for most of the first. He managed to open a cut around Lesnar's right eye early in the round, but one punch was all it took to turn the tide.
As for what's next for Couture now that's he's lost his title, "The Natural" sounded optimistic.
"I still feel like I'm getting better. I made some mistakes and got caught."
• The co-main event of the evening was less competitive, with Kenny Florian cementing his place as number one lightweight contender thanks to a first-round submission victory over Joe Stevenson.
After adamantly insisting that he was not an underdog, Stevenson proved to be no match for the Massachusetts fighter. Florian was the more active fighter from the opening bell, out-maneuvering and outstriking Stevenson in the early going. A takedown midway through the first round was the opening Florian needed. He quickly gained the mount and used his striking from the top position to force Stevenson to give up his back. The rear naked choke finish followed at the 4:03 mark.
An emotional Florian called out lightweight title-holder B.J. Penn after the win.
"I want B.J.'s belt. I consider [Penn] a master. It's time to kill that master."
• Dustin Hazelett put in another technical performance with a first-round submission of Tamdan McCrory. Though the fight was fairly even on the feet in the opening minutes, it was long before Hazelett got things to the ground and secured an oma plata shoulder lock during a scramble. McCrory defended well, but Hazelett transitioned into a straight arm lock that looked close to hyperextending McCrory's elbow, forcing him to tap.
• Heavyweight Gabriel Gonzaga overpowered UFC newcomer Josh Hendricks, manhandling him in the clinch before eventually connecting with a solid right hand that left Hendricks face down on the mat just over a minute into his UFC debut. After the bout, Gonzaga made it clear that he still has his sights set on the heavyweight title.
"I want a title shot, and next time I'm going to get the belt," Gonzaga said.
• Jiu-jitsu ace Demian Maia continued his impressive climb up the UFC's middleweight ladder with a quick rear naked choke finish against Nate Quarry. Maia wasted no time in getting the fight to the mat and once there simply outclassed Quarry. Maia looked yet again like a potential future champion, but seemed to be setting his sights lower in the post-fight interview.
"It's up to Dana White and Joe Silva," said Maia. "There are many tough guys. Maybe Michael Bisping is a good fight for me."
• Jorge Gurgel and Aaron Riley turned in one of the night's most exciting fights on the preliminary portion of the card. The two mixed it up on the feet for three rounds, with Gurgel punishing Riley with body kicks early on but eventually fading behind and aggressive, varied attack from Riley that earned him the unanimous decision victory.
• Rafael Dos Anjos controlled Jeremy Stephens for most of their bout and looked to be headed to a decision win of his own, until Stephens unleashed a right uppercut early in the third round that dropped the Brazilian. A few extra punches sealed the deal for Stephens, who celebrated the come-from-behind, knockout victory by hurling his body against the Octagon fence.
• Canadian Mark Bocek outgrappled Alvin Robinson in their lightweight contest, dominating the fight before eventually locking in a rear naked choke to force the submission.
• Former Ultimate Fighter contestant Matt Brown notched his second UFC victory after losing the first round to a very tough Ryan Thomas. After several unsuccessful submission attempts from his back, Brown eventually secured an armbar from the guard that Thomas was unable to escape.