And while the Waterford man had to leave Old Trafford to further his career, he believes that young Dubliner Robbie Brady has the ability to go all the way at United -- once he proves himself in games when given a chance.
"He has a fantastic left foot and he's very creative as the manager has already spoken about and he'll get another chance tonight to show that," said O'Shea, as he prepares to line out alongside Brady in the Irish side against Greece tonight.
"He has the potential but he also needs to get a long run of games to show that he is capable of playing at that level, showing his talent as he did last season.
"He got a few chances in pre-season and in the League Cup with United.
"Robbie is a very intelligent lad, he's under no illusions. He knows he's facing a very difficult task.
"But he has a lot of ability and the talent to back it up. If he did get a chance in the Manchester United team I'm sure he'd take it with both hands, but he has a lot of competition," added O'Shea.