Sexton took over the reins at Stamford Bridge from Tommy Docherty in 1967 and led Chelsea to a first FA Cup title in 1970 and a maiden European trophy the following season with victory over Real Madrid in the Cup Winners' Cup final.
Sexton went on to manage Manchester United, again succeeding Docherty, while he also took QPR to within a point of a first top-flight title before spending much of his later career with the Football Association.
But it is for his exploits with Chelsea that he will be best remembered, and Harris, who played nearly 800 games for the Blues in the 1960s and 70s, praised his formidable coaching skills.
The 68-year-old said: "It's a sad day, especially for the players that played under him. He used to spend hours on the training field. He was the best coach I ever worked with. I've got some great memories."
In contrast to Docherty, Sexton was a calm and methodical man who was renowned for a technical approach to coaching that saw him appointed the FA's first technical director at Lilleshall in the 1980s.
Harris said: "Dave was a very honest man who would pat you on the back. He came across as a bright lad. You knew when he was upset, you could see it in his face.
"He came from a boxing family and I don't think anyone would have taken him on in the boxing ring."
As well as his successes at Chelsea, Sexton also led the England Under-21 side to back-to-back European titles in 1982 and 1984, while his playing career included spells with West Ham, Luton, Leyton Orient, Brighton and Crystal Palace.
The FA's director of football development, Sir Trevor Brooking, said: "It is a sad day for English football.
"Anyone who was ever coached by Dave would be able to tell you what a good man he was but, not only that, what a great coach in particular he was.
"In the last 30-40 years Dave's name was up there with any of the top coaches we have produced in England - the likes of Terry Venables, Don Howe and Ron Greenwood. His coaching was revered."
There was a minute's applause before today's Premier League match between Chelsea and Manchester City at Stamford Bridge, and the Blues paid their own tribute to Sexton, who was given an OBE for services to football in 2005.
"Chelsea Football Club would like to express our enormous sadness and send our deepest condolences to the family and friends of Dave Sexton, who has died aged 82," the statement read.
"Sexton is without doubt one of the greatest managers in Chelsea history having led the club to our first FA Cup in 1970 and the Cup Winners' Cup a year later - our first European trophy."
Peter Bonetti, the Chelsea goalkeeper during the Sexton era, told chelseafc.com: "He was fantastic, I've got nothing but praise for him.
"He passed away peacefully last night. I've spoken to his wife and it's come as a complete shock because he was such a lovely man.
"Everybody loved him and everybody respected him here at Chelsea and he will go down in the club's history as being such a fantastic guy who brought us so much success.
"He was a football fanatic. It's so sad and I really can't believe it. Everything he did was fantastic, the fact we won the FA Cup in 1970 was a big memory."
QPR also expressed their sadness at Sexton's death, saying in a statement: "The club is desperately saddened to learn of the passing of former QPR manager Dave Sexton.
"The 82-year-old was appointed at the Loftus Road helm in October 1974 and adopted an unforgettable side, featuring the likes of Stan Bowles and Gerry Francis.
"Sexton was just a point shy of guiding Rangers to the 1975/76 league title - a position that still remains the club's highest league finish.
"The club would like to extend its deepest condolences to Dave's family and friends at this sad time. May he rest in peace."