LAS VEGAS — There's only so much relief a cold compress, sips of water and a cornerman waving a torn piece of cardboard over you can provide.
B.J. Penn, after taking a relentless beating on the mat for the final three of the four rounds he lasted against Georges St-Pierre, succumbed to a technical knockout stoppage by a ringside doctor and his corner before the fifth round began in Saturday night's showdown between the two Ultimate Fighting Championship belt-holders.
St-Pierre (18-2) defended his welterweight belt against lightweight champ Penn (13-5-1) by imposing his size advantage against the gutty UFC veteran who was unable to call upon his Brazilian jujitsu and striking strengths because of St-Pierre's repeated takedowns and extended barrages of punches and elbows. Penn routinely found himself with his back on the mat, and his face sometimes pressed into the octagon's chain link.
St-Pierre, thrilling a supportive capacity crowd of 14,885 at MGM Grand Garden Arena, was taking it to Penn in such a one-sided manner late in the final round that the crowd's quiet was shattered ringside by the thunder-like sound of Penn's head getting pounded into the mat.
Penn stood after the abuse, hung on the cage while standing in his corner and soaked in the comfort of the cold pack, water and fanning.
But William Berliner, the ringside doctor, and Penn's cornermen had seen enough, agreeing almost simultaneously that the fight should end and Penn's bid to become the first UFC fighter to hold two belts simultaneously was over. Penn then sat down, exhausted. He was later taken to a hospital for precautionary reasons.
St-Pierre had enthusiastically punctuated his fourth-round dominance by punching the cage with his left glove, and he then raised both arms when he realized the fight was over. Less than three years after first beating Penn by split-decision, St-Pierre produced a more pronounced triumph and earned $400,000 and bonuses.
"This time, I wanted a knockout, and I'm glad I did it," he said afterward.
Following a nearly even first round void of takedowns, St-Pierre got atop Penn just over a minute into the second round and stayed there, delivering punches that were made more intense by his rises off Penn's body and surges back on him with harsh blows.
Early in the third, Penn was cut under the left eye and his nose was bleeding. Penn's best moments were only a soft touch from his back and an occasional attempt to break free. He did get loose for less than a minute in the third, but less than 30 seconds into the fourth he was in the same vulnerable position again.
St-Pierre showed no mercy, an onslaught that probably would have generated a stoppage if this wasn't a double-belt fight and the defeated wasn't Penn.
Afterward, St-Pierre was met in the ring by his future opponent, Thiago Alves, who somehow managed to say he was excited about being next.
In the main undercard fight, unbeaten light-heavyweight Lyoto Machida (14-0) established himself as worthy for a title shot against champion Rashad Evans by knocking out Brazilian countryman and previously unbeaten Thiago Silva (13-1) in the final second of the first round.