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).