Sources: Mirko Filipovic-Roy Nelson set

A heavyweight fight between Mirko Filipovic and Roy Nelson has been booked for the UFC 137 card Oct. 29 in Las Vegas, sources told ESPN.com on Wednesday.

Filipovic first broke the news to a Croatian sports show Tuesday.

Both fighters have struggled as of late, combining for zero wins in their last four contests.

After beginning 2010 with back-to-back wins, Filipovic (27-9-2) has suffered brutal knockout losses to Frank Mir and Brendan Schaub during the last 10 months.

Following the third-round loss to Schaub at UFC 128 in March, Dana White speculated it was time for the 36-year-old to retire. The UFC president has softened his stance since, saying, "I owe him another fight."

Nelson (15-6) is looking to avoid dropping three straight fights for the first time in his career. Winner of the tenth season of "The Ultimate Fighter" reality series, the former IFL champion won his first two fights in the UFC before coming up short in decision losses to Junior dos Santos and Mir.

White was particularly critical of Nelson's performance against Mir at UFC 130 in May, calling it both "terrible" and "embarrassing." Nelson was visibly winded early in the fight but was diagnosed with walking pneumonia.

UFC 137 will take place at Mandalay Bay Events Center. A welterweight title fight featuring Georges St. Pierre and Nick Diaz is scheduled to headline.

Brett Okamoto covers mixed martial arts for ESPN.com.