#1 Jaap Stam: Everything!
The biggest regret of Sir Alex Ferguson's managerial career was selling Japp Stam to Lazio because he thinks this guy is on par with Milan legends Franco Baresi and Paolo Maldini. That says something, doesn't it?
In his three seasons at United, Stam won the Premier Leauge in each of them along with the FA Cup and Champions League as a part of the treble in the 1998-99 season and Inter-continental Cup in 1999.
6 foot 3 inches and hard as a rock, he was known for possessing a rare combination of speed, strength and ball-playing ability as well as an excellent positional sense. With him at the back, United rarely conceded goals. He is one of the rare professionals who could mix finesse with solidity.
United defensive unit should watch videos of the great man to get an insight into the art of no-nonsense defending!