The main event for UFC 311 has been dramatically changed just 24 hours before Saturday's card in California.

Lightweight champion Islam Makhachev was due to defend his title against Armenia's Arman Tsarukyan.

But Tsarukyan has now pulled out of the title bout due to a back injury. 

The UFC have wasted little time in finding a replacement, with Brazil's Renato Moicano stepping in to challenge Makhachev for lightweight gold.

UFC president Dana White announced the news on Friday in a social media video. White said: 'Around 1am we received a call from Arman Tsarukyan who informed us that he was experiencing significant back pain. Due to the injury, he feels like he is not healthy enough to compete. So, he is out of the fight.

'Stepping in to face Islam Makhachev for the title will be Renato Moicano. He weighed in on championship weight to be prepared as the back-up in case something happened, and when we spoke to him this morning, I can tell you, he wants this fight.

'And when I called Islam, Islam said "Brother, I am the champion. I don't care who it is, I will fight anyone".'  

Moicano, 35, has an MMA record of 20 wins, five losses and one draw.

He has won six of his last seven fights, with five of those victories coming inside the distance. 

But he faces a tough challenge to get past Makhachev, who is widely viewed as the No1 pound-for-pound fighter on the planet. 

Makhachev has only lost one of his 27 professional bouts and is currently on a 14-fight winning streak.