Lightweight contender Donald "Cowboy" Cerrone has agreed to replace Sam Stout in a matchup against Dennis Siver at UFC 137 in October.

Stout is dealing with the unexpected passing of his longtime trainer and brother-in-law Shawn Tompkins earlier this month. UFC officials confirmed the switch to ESPN.com Monday.

It will be the fourth trip to the Octagon this calendar year for Cerrone (16-3), matching the most in his career. Cerrone is currently riding a five-fight win streak, including an impressive first-round TKO over Charles Oliveira on Aug. 14.

The Greg Jackson product is 0-3 in title fights, but a perfect 16-0 otherwise.

Siver (19-7) also looks to strengthen his case for a run at the title. The German lightweight has won four straight and eight of his last nine.

He turned in a terrific performance at UFC 127 in February, scoring an upset win over George Sotiropoulos in Australia. In his last fight, Siver won a somewhat controversial decision over Matt Wiman at UFC 132.

The UFC 137 event takes place at the Mandalay Bay Events Center in Las Vegas. A welterweight title fight between Georges St. Pierre and Nick Diaz is scheduled to headline.