Robbo says United manager Sir Alex Ferguson never bases a team selection on reputation.
He told the Mail on Sunday: "I'd won the title in '93 and '94 and we'd reached the FA Cup final in 1994 against Chelsea. I'd already agreed to go to Middlesbrough as player-manager the following season, so I thought, 'What a way to leave United by winning the Double'," said Robson. "I'd played in loads of cup-ties that season and scored in the semi-final against Oldham. We get to the final at Wembley and I'm not even a sub.
"I was gutted but that is what the man is about. He makes real tough decisions and, going into management myself later, I know that those are tough decisions.
"When you get to a cup final you want to look after everybody, but you can't. He said to me when he made that decision, 'I've got Nicky Butt coming through. I think a lot of him. I'm going with him on the bench, not you'.
"I told him, 'I've scored a goal in the semi-final. We won 4-0, we're in the final and we've won the league, where's the justice in that?'. He just said, 'That's my decision', so you've got to accept it. That is what makes him a winner because he makes hard decisions like that.
"OK, it doesn't make him favourable with everybody, but that's what makes him successful. He has this aura about being a winner."