Tony Cascarino believes Roy Keane never hit the levels for Ireland that did for Manchester United.
The former Ireland striker picked the Corkman as the second best player he played alongside in his career.
But despite heaping praise on Keane, Cascarino thinks the United captain didn't excel as much in a green shirt.
He told TalkSport: [Keane] was a terrific footballer, but he never played as well for Ireland as he did for Manchester United.
"I don't mean he played poorly for Ireland. I think there were games there - Holland, for example, when he was tremendous when we beat them 1-0.
"He was Fergie's best player for a number of years. He was the outstanding player for Fergie and that's why he led and drove the team.
"He would inspire you just with his performances."
Cascarino pitched in another Corkman in Denis Irwin in his top five along with English duo Steve Bruce and Teddy Sheringham.
But there was no doubt in his mind about who was the best player he ever lined up with.
"My number one is the obvious one because still to this day, I don't know how a player who could have lived his life the wrong way - everything you're not meant to be - it had to be McGrath.
"Paul was just tremendous. He was a great athlete and the reason why Sir Alex Ferguson got him out of Old Trafford and it's been well documented was because of the culture at the football club and the drinking.
"Paul was a bit of a follower, he wasn't a leader, he just followed people and got into bad habits.
"Fergie always said he never questioned his ability, because he would have loved Paul McGrath when he was fit and the way he could play, his athleticism, his heading ability.
"Paul was just amazing to watch from the sidelines, not only in training.
"Very few people got the better of him. I can't remember going 'you know what Paul got a really rough time there'".
