Last October, Conor McGregor revealed that he was actually fighting Chad Mendes injured during their main event scrap at UFC 189, three months prior. "The Notorious" had supposedly torn "80 percent" of his ACL fourteen weeks prior to fight night, claiming he could barely walk and barely kick during those times. He did end up winning the fight, but was still heavily criticized for being easily taken down by Mendes.
The manner of which McGregor sustained the injury was never really explained, until Kavanagh gave the details in his new autobiography "Win or Learn" (as reported by The 42).
"Artem explained that Conor and Rory MacDonald – a Canadian welterweight who was scheduled to take on the champion, Robbie Lawler, in UFC 189 – had been training together that afternoon Nothing strenuous, just a bit of grappling. But during their session, Rory landed awkwardly on Conor’s left knee – the same knee he had injured against Max Holloway," Kavanagh wrote.
Kavanagh says he urged his fighter to get himself checked, but McGregor insisted that he "could get by" without any form of surgery. Instead, he opted for stem-cell therapy.
"He flew straight out to Germany and was given stem-cell injections into his knee. Within a few days, he was back in the gym. ‘It feels good,’ he insisted. ‘It’s not perfect but it’ll get better over the next few weeks of training. Let’s do this. I’m ready.’"
"And that was that. We were going full steam ahead for the biggest fight in UFC history in spite of a knee injury the seriousness of which was unclear."