Ahead of today's FA Cup tie, O'Shea believes the midfielder must now discover consistency.
"I remember Paul from the youth team. He was so bubbly, everybody knew he was a fantastic talent. He will be a huge star for United because there's that ability. And once he concentrates on that, he'll be a fantastic player for years to come. He won the World Cup, so he's doing enough talking on the pitch, but he's got to make sure he keeps doing it.
"The best players maintain that level consistently season after season, and the attributes that he has, if he can maintain that, he will become like he's showing at the minute — that player who scores goals, creates goals. And if he does that I'm sure the United fans will get right behind him."