MATTHEW HARDING
Given the successes of Chelsea since 2003, his role has become unfairly overshadowed. However, it's arguably due to the late Matthew Harding that Chelsea became a major world force.
Chelsea in the 1980s and early 1990s was a different club to today. It often flirted in the relegation zone, got relegated, and their stadium was also a greyhound running track. It was a poor in relation to other London clubs, especially at that point Arsenal and Tottenham Hotspur.
With the advent of the Premier League, the then club owner Ken Bates and Harding devised plans make Chelsea more competitive. This included a stadium revamp, new club facilities, and better players. Ruud Gullit signed from Italy, and Mark Hughes came from Manchester United. Glenn Hoddle had joined as manager in 1993, and the club looked to move forward to eventually enter the English footballing elite.
This ended in tragedy, however, as Harding died in a helicopter crash in autumn 1995. He eventually held the freehold of the Stamford Bridge ground (but didn't own the club overall, as Ken Bates did). But his legacy is that he helped Chelsea on the initial foundation steps of being a large global football club. He helped spring Chelsea into the big-time, by reorienting its attitude, focus, and ambitions.
The 1997 FA Cup win vs Middlesbrough was dedicated to his memory, and in tribute to making Chelsea a competitive team again.