Former Manchester United defender Gabriel Heinze says he was once knocked unconscious by Roy Keane during their time together at Old Trafford.
Heinze shared his recollections of Keane in an interview with ESPN Argentina's "Pura Quimica," describing how he and the then United captain came to blows shortly after he joined from Paris Saint-Germain in 2004.
The ex-Argentina international said: "We went to Middlesbrough and we ended up losing 2-1. The team was disastrous. To be honest, I thought I had not played that badly.
"I'm the first one off the pitch when a game ends because I don't like to talk to anyone. I went straight to the changing room -- I was the first in and Roy was next. I didn't speak much English then.
"I see that he [Keane] is staring at me and he says 'f--- off.' I knew that swear word because those are the first things you learn. He comes towards me and I tell him 'f--- off you,' and that is the last thing I remember. I didn't even have time to swing my arm..."
Heinze said Keane's temper was well known at United.
"[Then-manager Six Alex] Ferguson called me up and told me that he knew what had happened," he said. "I asked him if I needed to apologise... I mean he was the biggest idol of Manchester United's history.
"He [Ferguson] said, 'no, Roy was like that.' But he told me not to worry because Roy had already forgotten about that episode.
"We went to training and I was very scared. I remember we both went for a ball and I was ready for anything but as the action happened Roy told me, 'beware -- what happens on the pitch stays on the pitch and what happens in the changing room ends there.'"
Heinze bears no grudge against Keane, who is the current assistant manager to Republic of Ireland coach Martin O'Neill.
"I've had an excellent relationship with him since that episode," the 39-year-old said. "He is an extraordinary man. He was one of the best captains the club ever had."
Keane is the most successful United captain ever, winning 10 major trophies, while he won seven Premier League titles in total as a player.