Kamaru Usman will face Khamzat Chimaev in the co-main event of UFC 294, after replacing Paulo Costa on 10 days’ notice. Usman, who reigned as welterweight champion from 2018 until 2022, will make his middleweight debut in the bout, which pits him against one of the most dominant prospects in mixed martial arts. Swedish-born Russian Chimaev is 12-0 as a professional with 11 stoppage wins. The match-up was confirmed on Wednesday (11 October), when Costa revealed that he would need two elbow surgeries this week, having already undergone one two weeks ago. As such, the Brazilian is out of UFC 294, which takes place in Abu Dhabi on 21 October. The 32-year-old’s withdrawal was the second by a Brazilian in the space of two days; on Tuesday (10 October), Charles Oliveira withdrew from the main event of UFC 294 due to a severe cut over his right eye. Oliveira was due to challenge Islam Makhachev for the lightweight title in a rematch – 12 months after the Russian submitted him in the same venue in Abu Dhabi. Alexander Volkanovski, who holds the featherweight title, is stepping in to replace Oliveira and contest his own rematch with Makhachev, who narrowly outpointed him to retain the lightweight belt in February. Usman, 36, last fought in March, suffering a decision loss to Leon Edwards while challenging for the welterweight title, which Edwards took from the Nigerian-American with a brutal head kick last August. Chimaev, 29, last fought in September 2022, submitting Kevin Holland in Round 1. Chimaev was originally set to face Nate Diaz on that occasion but missed weight, leading the card to be altered on short notice. Diaz instead fought and submitted Tony Ferguson in the main event. Click here to subscribe to The Independent’s Sport YouTube channel for all the latest sports videos. Read More Usada ends UFC partnership over ‘untenable’ Conor McGregor situation Charles Oliveira replaced by Alexander Volkanovski in Islam Makhachev fight UFC schedule 2023: Every major fight happening this year