UFC 137: Penn vs. Diaz was an event held by the Ultimate Fighting Championship on October 30, 2011 (aus time) at the Mandalay Bay Events Center in Las Vegas, Nevada.
Diaz, who was originally scheduled to headline the card opposite Georges St-Pierre for the UFC Welterweight Championship, was pulled from the fight on September 7, due to failing to make media appearances.
On September 8, B.J. Penn announced via Twitter that Dana White offered him a fight he “cannot refuse”. Later that day, both Penn and White announced that the fight would be against Nick Diaz.
Georges St. Pierre was expected to defend his title against Carlos Condit on this card, but had to withdraw due to knee injury. Nick Diaz vs. B.J. Penn was promoted to the main event.
Here are the results from the main card:
Tyson Griffin vs. Bart Palaszewski
Palaszewski defeated Griffin via KO (punches) at 2:45 of round 1.
Dennis Siver vs. Donald Cerrone
Cerrone defeated Siver via submission (rear naked choke) at 2:22 of round 1.
Hatsu Hioki vs. George Roop
Hioki defeated Roop via split decision (29–28, 28–29, 29–28).
Scott Jorgensen vs. Jeff Curran
Jorgensen defeated Curran via unanimous decision (29–28, 29–28, 30–27).
Mirko Filipović vs. Roy Nelson
Nelson defeated Filipović via TKO (punches) at 1:30 of round 3.
Cheick Kongo vs. Matt Mitrione
Kongo defeated Mitrione via unanimous decision (30–27, 30-28, 29–28).
BJ Penn vs Nick Diaz
Diaz defeated Penn via unanimous decision (29-27, 29-28, 29-28)