Former WEC lightweight title challenger Donald “Cowboy” Cerrone will step in to face Dennis Siver at UFC 137 on October 29th in Las Vegas, Nevada. Cerrone replaces Sam “Hands of Stone” Stout, who withdrew from the fight. MMAWeekly.com first reported on the change to the matchup on Monday.

Stout confirmed to The MMA Show today that his withdrawal from the bout comes as a result of the recent loss of long-time trainer and brother-in-law Shawn Tompkins, who passed away earlier this month. Both Cerrone and Siver, top contenders at 155, are currently on lengthy winning streaks.

Cerrone (16-3-0, 1 NC) has already fought three times in the UFC this year since making his debut in February. The submission specialist has posted impressive victories in each Octagon appearance to date and most recently earned the first knockout victory of his career by stopping Charles “do Bronx” Oliveira at UFC Live 5 on August 14th. Of Cerrone’s 16 pro wins, 12 have come by submission, and he holds notable victories over Jamie Varner and Chris Horodecki. All three of Cerrone’s losses came in WEC Lightweight Championship bouts.

Siver (19-7-0) has won eight of his last nine fights since suffering the lone knockout loss of his career against Melvin “The Young Assassin” Guillard in 2008. The German kickboxing standout has stopped 14 opponents to date and possesses a solid ground game to complement his technical striking skills. Siver has scored a pair of big victories in 2011; first earning a decision over George Sotiropoulos in February and later escaping with a razor-thin win over “Handsome” Matt Wiman last month. A win over Cerrone would put Siver on a short list of title contenders.

A timetable for Stout’s return is not yet known, as he and his teammates mourn the loss of their trainer and friend. The close-knit team is expected to remain together.

UFC 137 takes place on October 29th at the Mandalay Bay Events Center in Las Vegas, Nevada. The event will be headlined by a UFC Welterweight Championship bout between Georges “Rush” St. Pierre and Nick Diaz.

UFC 137 Fight Card (to date; subject to change):

– Georges “Rush” St. Pierre vs Nick Diaz [UFC Welterweight Championship]
– “The Natural Born Killer” Carlos Condit vs “The Prodigy” B.J. Penn
– Matt Mitrione vs Cheick Kongo
– Mirko “Cro Cop” Filipović vs Roy “Big Country” Nelson
– Donald “Cowboy” Cerrone vs Dennis Siver
– Hatsu Hioki vs George Roop
– Brandon “The Truth” Vera vs Eliot “The Fire” Marshall
– Tyson Griffin vs Bart “Bartimus” Palaszewski
– “Crazy” Tim Credeur vs Brad Tavares
– Scott “Young Guns” Jorgensen vs “The Big Frog” Jeff Curran
– Danny “Boy” Downes vs Ramsey Nijem

(Photo Credit: Sherdog.com)