#2 Mark Hughes
The former Stoke manager is known mainly known for representing Manchester United for 6 seasons between 1989 and 1995. He was signed by Sir Alex for €2.75 million in July 1989. He went on to score 88 goals and provide 17 assists in 247 games for the Red Devils. The stint brought 2 league titles and a host of domestic trophies.
What's remarkable is that this was his second stint for United. He was sold to Barça for €3 million in July 1986 before being brought back. Out of 3 seasons in Spain, he was loaned to Bayern Munich for 1 season. In the remaining 2 seasons, he scored 5 goals in 35 matches for the club. While his stay at the club coincided with Lineker's, Hughes wasn't as successful as his compatriot.
Regardless of his performances at Barça, Sir Alex saw it fit to bring him back. The punt paid off as he played a key role in the success that followed. Barcelona, Bayern Munich, Manchester United and Chelsea are just some of the clubs on Mark Hughes' CV.