5. Roy Keane
At the club: 1993 - 2006
Appearances: 480
Goals: 51
Honours: 7 x Premier League; 4 x FA Cup; 1 x UEFA Champions League; 1 x Intercontinental Cup
"Aggression is what I do. I go to war. You don't contest football matches in a reasonable state of mind"
He went to war and he rarely lost. Roy Keane was arguably the greatest leader to have donned the red of United - his never-say-die, blood-and-thunder attitude permeated through the team and his champion attitude reflected in everything the team did as a collective.
Remembering him for how tough he was, and how much of a winner he was ("If I was putting Roy Keane out there to represent Manchester United on a one against one, we'd win the Derby, the National, the Boat Race and anything else," Sir Alex Ferguson once said. "It's an incredible thing he's got."), is doing a disservice, though, to just how good a footballer he was.
It wasn't just the ball-winning that mattered, but his metronomic and intelligent passing set the rhythm of the team in a way that most people overlooked due to the nature of the man himself.
Think about it - the one player that United have never been able to replace in the modern era is Roy Keane... and it isn't just that unique attitude they have been missing.