It's safe to say Penn isn't calling it quits anytime soon.
Instead, the Hawaiian mixed martial arts legend provided a rejuvenating jolt to his already-storied career, knocking out former two-time welterweight champion Matt Hughes in just 21 seconds before 16,404 fans at The Palace of Auburn Hills.
"I honestly don't want to sit here and beat my chest over beating Matt," Penn told MMA Fighting after capturing the rubber match of the trilogy. "He's just another guy like me who's been around the sport a long time. I'm very fortunate things went the way they did tonight. Besides that, I don't want to harp on anything else."
Penn caught Hughes with an overhand right that knocked Hughes on his back before landing four more punches that put the UFC Hall of Famer out. Recreating a moment early in his career when he knocked out Caol Uno in just 11 seconds, the joyous Penn sprinted out of his cage and headed back towards the locker room before returning.
"When I was walking out, my coaches grabbed my arm and said that I had to go back and get my hand raised," Penn said. "I said, 'You know what? I've gotta go back. It would be disrespectful to Matt, so I've got to do the honors."
In the cage, Penn called Hughes his idol.
Afterward, White said Penn (16-7-1) would face Jon Fitch in Australia in the main event of UFC 127. Fitch had been scheduled to face Jake Ellenberger, but the UFC called an audible after Penn's riveting win.
The bout ended an epic rivalry nearly seven years in the making, with Penn capturing the series nearly seven years after his submission win over Hughes at UFC 46 gave him his first UFC championship. Hughes won the UFC 63 rematch via TKO to even the series before Saturday.
"I was in there to fight," Penn said. "I wanted him to hit me and I wanted to hit him and I was in the mindset of 'fight like a kid.' I got in this to fight. I had a lot of people questioning me and that motivated me and I wanted to do this. I wanted to show people my fighting spirit and what I was about."
Meanwhile, another cage legend also rebounded with a win, as Quinton "Rampage" Jackson turned back the clock with an aggressive game plan that led to a split decision over Lyoto Machida.
Jackson took the fight to Machida, moving forward with strikes while Machida chose to counter with leg kicks. Jackson outstruck Machida in each of the first two rounds, outlanding him 25-12 in round one and 21-9 in round two according to Compustrike scoring.
Machida rebounded by dominating the third, hurting Jackson with a combo that started with a left hook and knees to the body. Machida took Jackson down and worked him over for most of the rest of the round, but two of the three judges felt Jackson did enough to capture the bout.
In the seconds after the fight, Jackson said Machida whipped him, but in the post-fight press conference, he said he got carried away with his statements after suffering through a rough final round.
"I had just gotten done getting punched in the face a few times," Jackson said. "My trainers and everybody said I won the fight. I have a one track mind and I wanted to knock him out. He dominated me so much in the third I forgot I won the first two rounds. My trainers said it, Dana reminded me. I was just getting off the ground and he ran a flurry in my face."
The victory puts Jackson back in the title mix while the once-unbeatable Machida is now a loser of two straight.
George Sotiropoulos continued his march up the lightweight ladder, extending his unbeaten streak in the octagon to seven straight with a second-round submission win over Joe Lauzon.
The two engaged in a very close first round, with Lauzon landing power punches and Sotiropoulos looking to take the fight to the ground, getting in there on a few occasions. But Lauzon waded his way out of trouble and looked like he was going to give Sotiropoulos a tough, grinding fight.
But in the second, Lauzon wasn't the same fighter. Whether he suffered an injury or simply ran out of gas seemed unclear, but Sotiropoulos took over from nearly the beginning of the round, at one point punishing Lauzon with knees to the head from a clinch. He soon got the fight to the ground and forced Lauzon to tap with a kimura.
"It was the calm before the storm," Sotiropoulos said of the first round. "I went into the storm and I found my range."
Now 14-2, Sotiropoulos can't be too far from moving deep into the title picture, and he asked to be considered into that group of contenders.
"I want to face the best," said Sotiropoulos, whose effort helped win the Fight of the Night award, worth $80,000. "I want to make a case for the belt. That's the goal. That's the destination and I'm going to continue making my case."
Later, White said Sotiropoulos would next face Dennis Siver.
Light-heavyweight prospect Phil Davis had his first time on the main card spotlight at UFC 123, and he answered the call by placing his unique stamp on the night, essentially inventing his own submission in his second-round defeat over Tim Boetsch.
Davis modified a kimura by cranking on with both of his arms under the near side of Boetsch's back for the fight-ending submission.
"I kind of make moves up as I go," Davis said after moving to 8-0. The unusual maneuver earned him an $80,000 Submission of the Night bonus.
Davis sailed through the first as well, taking Boetsch down with a slam and punishing him with punches to the body and short elbows to the head.
The win capped off a banner stretch for Davis, who debuted in the UFC in February and won four fights during the calendar year.
In the night's other main card fight, Maiquel Falcao debuted with a decision win, ending Gerald Harris' three-fight win streak.
The fight was far from a crowd-pleaser, punctuated by long stretched of inactivity in the first and third rounds. But when they did engage, Falcao asserted his standup dominance by hurting Harris several times, and he stuffed most of his takedown attempts, leaving Harris with few ways to win.
Falcao captured both of the first two rounds, but did almost nothing in the third, cruising through the final five minutes as the crowd rained down boos on the pair. According to Compustrike, Falcao threw just seven strikes the entire round, content to protect his lead.
White was not happy with the final round performance, but said he'd give Falcao "the benefit of the doubt" since it was his first UFC fight.
"It's his first UFC win but this isn't the Ultimate Staring Competition, it's the Ultimate Fighting Championship," White said. "That's not what people want to see."