Usman replaces Costa, will fight Chimaev at UFC 294

Kamaru Usman has stepped in for the injured Paulo Costa and will face Khamzat Chimaev at middleweight in the UFC 294 co-main event on Oct. 21 in Abu Dhabi, United Arab Emirates, UFC president Dana White announced Wednesday.

Costa underwent surgery on his right elbow three weeks ago to treat an infected bursa, he revealed Monday. The former title challenger, who has been in Abu Dhabi for the past four weeks, said on "The MMA Hour" that he "definitely" still intended to fight Chimaev. But Costa wasn't medically cleared by doctors.

Costa tweeted Wednesday that he is once again in hospital and underwent a second surgery Tuesday. He added doctors told him he will need to undergo a third procedure Friday.

Usman, the former UFC welterweight champion, will be making his 185-pound debut against Chimaev. The 36-year-old will also attempt to snap a two-fight skid. Usman lost the title to current champ Leon Edwards by fifth-round knockout in August 2022 and then fell short via majority decision in their March trilogy bout.

Chimaev hasn't stepped into the Octagon since submitting Kevin Holland in a welterweight bout in September 2022. Chimaev was scheduled to face Nate Diaz in the UFC 279 main event but badly missed weight and ended up booked against Holland instead. Chimaev is 6-0 in the UFC and will be competing in his first middleweight fight since 2020.

White told Yahoo Sports' Kevin Iole that the winner between Chimaev and Usman will be next in line to challenge Sean Strickland for the middleweight title.

Usman and Chimaev are ranked Nos. 1 and 4 in the welterweight division but unranked at 185 pounds.

UFC 294 will feature a lightweight title rematch between defending champion Islam Makhachev and featherweight titleholder Alexander Volkanovski. Volkanovski stepped in on 11 days' notice after Charles Oliveira pulled out due to injury.