UFC 137 results and recap: Diaz calls out GSP, Penn and Cro Cop announce retirement

Nick Diaz took B.J. Penn to a brutal decision at UFC 137, winning what Penn said during his post-fight interview was The Prodigy's last dance in the Octagon. "This was probably the last time you'll see me in here. I can't keep performing at the top level," Penn said. "I've got a daughter and another daughter on the way. I don't want to go home looking like this. I'm done." Despite hanging his gloves on a loss, Penn put on an electrifying show, displaying the fantastic boxing, slick grappling and violent fighting spirit that made him one of the biggest names in all of MMA. The former lightweight and welterweight champ out boxed Diaz and took his back in the first frame but eventually wilted to Diaz's superior cardio and relentless, dominating offense in rounds two and three. The final round especially was a treat for Penn fans. Often criticized for a half-empty gas tank and a sometimes questionable heart, Penn met Diaz in the center of the ring and both men could barely be held back by the referee at the start of the round; Penn, though clearly losing the frame, came out aggressively and fought hard on fumes until the bell sounded. Despite the L, it was a fine final chapter for the Hawaiian legend's storied career and a solid choice for Fight of the Year. In a memorable post-fight promo, Diaz, still high off the blood in the water, paid his respects to Penn and brusquely called out Georges St. Pierre, saying the welterweight champion was scared to fight. (It worked. The UFC has since announced that number one contender Carlos Condit has willingly stepped aside to let GSP and Diaz settle their differences on Super Bowl weekend.) MMA legend and Pride 2006 Open-Weight Grand Prix champion Mirko "Cro Cop" Filipovic also retired last night, after his third loss in a row. A slimmed down Roy Nelson withstood a flurry of heavy leather in the second round and even survived a Cro Cop head kick to secure a TKO victory in the third. UFC 137 featured a number of slow-paced fights and lacked the original headliner, GSP, who pulled out from his fight with Condit due to injury. Amid the overall underwhelming card, however, Donald Cerrone was able to stand out with another another impressive performance, taking out touted contender Dennis Siver in the first round with astonishing authority. Full results and a slice of Diaz's offensive onslaught below. Nick Diaz def. B.J. Penn via unanimous decision Cheick Kongo def. Matt Mitrione via unanimous decision Roy Nelson def. Mirko Filipovic via TKO (strikes), round three Hatsu Hioki def. George Roop via split decision Scott Jorgensen def. Jeff Curran via unanimous decision Donald Cerrone def. Dennis Siver via submission (RNC), round one Bart Palaszewski def. Tyson Griffin via TKO (strikes), round one Brandon Vera def. Eliot Marshall via unanimous decision Ramsey Nijem def. Danny Downes via unanimous decision Francis Carmont def. Chris Camozzi via unanimous decision Clifford Starks def. Dustin Jacoby via unanimous decision Image sources: SB NATION