Kamaru Usman defeated Colby Covington with a broken hand after the UFC welterweight champion revealed he suffered the injury three weeks out from fight night while sparring Justin Gaethje.

Usman, 34, earned a unanimous decision victory over arch rival Covington at UFC 268 in New York City, in which he floored the challenger in the second round but was unable to get the finish.

The Nigerian Nightmare's striking has come on leaps and bounds in recent years, largely due to the guidance of renowned trainer Trevor Wittman, who also trains Rose Namajunas and Gaethje.

And Usman has revealed that he sustained a broken hand three weeks before the fight at Madison Square Garden. 

'I broke it before the fight,' Usman told Full Send Podcast. 'Most people didn't know that. I broke it three weeks before and I didn't throw it a day until the fight itself.

'I didn't throw it until right backstage. I didn't throw my hands for three weeks, my right hand.'

The welterweight king lifted the lid on the cause of the injury, revealing that he broke his hand during a sparring session with lightweight contender Gaethje. 

'I broke it on someone's head,' he added. 'Justin Gaethje's head. We spar together. Same coach, main training partners-slash-big brother, little brother-slash-two assassins in the same place. He gets the better of me sometimes. Justin Gaethje's a savage.'

Usman and Gaethje trained closely in the lead up to UFC 268, with the 155-pounder preparing for his clash with Michael Chandler. The pair shared an exhilarating 15 minutes in the Octagon and their fight has been touted as a Fight of the Year contender.

For Usman, his inability to finish Covington inside five rounds left him 'disappointed', but he also notes that his rival's powers of recovery, added to his injured hand, meant it would be difficult to secure a knockout.  

'I was a little disappointed [that I didn't get the finish],' Usman said. 'It's weird, I was in the back and the whole time I just manifested, I'm like, "I'm gonna knock him out. I'm so much better than him now, I'm gonna knock him out."

'But what I realized too is that I haven't thrown my right hand in three weeks leading up to this fight. It takes timing. You have to really be clicking to really be able to find that shot, so this is gonna be the first time I'm throwing my right hand in three and a half weeks.

'So I get in the fight and I'm going, "Damn, I just can't find him with that right hand." But that's because my timing wasn't there, but the left hand I was finding him. 

'He's tough, he showed how tough he was. He was able to recover very quickly. I made him do the Stanky Leg a couple of times, but he was able to recover quickly and hold on and not get finished.'