LAS VEGAS, Nevada—Conor McGregor suffered a broken leg in another crushing defeat to Dustin Poirier at the T-Mobile Arena in Las Vegas on Saturday, with the fight stopped by doctors at the end of the first round. As a thrilling first five-minute frame drew to a close, both fighters were still trying to land as McGregor stumbled backwards, trapping his foot under himself and breaking his ankle. Medics were immediately called into the octagon and it was clear that McGregor could not continue, prompting referee Herb Dean to declare a stop to the bout on the instructions of the doctor. Interviewed in the octagon with his leg in a cast, McGregor raged about his misfortune. “I was boxing the head off him, kicking the leg off him, (he was doing) the usual, diving to close the distance. This is not over,” he said. With McGregor having won at featherweight in …