Roy Keane left a sport psychologist "shocked" just hours after the therapist began working at Manchester United.
Bill Beswick was brought to United by Alex Ferguson and went to watch a training session on his first day at the club.
Beswick was stunned by how Keane began shouting at fellow Corkman Denis Irwin after he failed to play the ball to him.
The psychologist told Keep It On The Deck: "The first day I went to Manchester United, I was watching eight versus eight possession.
"Roy Keane - who's a warrior, not just an athlete, not just a competitor but a warrior, the mindset of a warrior - his team have got possession.
"Denis Irwin has got the ball. He's looking up, he's trapped, he's going to lose the ball.
"Roy Keane makes a beautiful run and signals 'Denis!' where he wants the ball.
"Denis doesn't see him, doesn't hear him, doesn't respond and loses the ball.
"Roy Keane ran 40 yards to challenge his teammate: 'Get your head up.' I was shocked."
But Beswick was told by Ferguson how Keane's outbursts helped spur the team on.
"I was stood next to Alex Ferguson, the manager of Manchester United," Beswick added.
"He said son, 'Now you know why we win on a Saturday. We win on a Saturday because we have the mindset to train every day.'"
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