Renan Barao, the Ultimate Fighting Championship's bantamweight champion, will defend his belt against Cal State Fullerton product T.J. Dillashaw in the new UFC 173 main event May 24 at MGM Grand in Las Vegas.
UFC President Dana White finalized the bout as a replacement for the postponed middleweight title defense by champion Chris Weidman against former light-heavyweight champion Lyoto Machida.
Weidman last week suffered a knee injury that required minor surgery. Weidman-Machida will now be fought in July at Mandalay Bay in Las Vegas.
The 27-year-old Barao (34-1) won the belt in July 2012 by defeating veteran Urijah Faber and has successfully defended the belt three times, most recently by a first-round technical knockout of Faber in February.
Sacramento's Dillashaw (10-2) is the UFC's No. 5-ranked bantamweight. He responded to an October split-decision loss to No. 3 Raphael Assuncao by beating Mike Easton by unanimous decision in January.
The May 24 card also includes a heavyweight fight between former champion Junior Dos Santos and seventh-ranked Stipe Miocic (11-1).