How did John McEnroe lose his edge?

(My answer in Quora)

The common answer is to blame it on 1986. The year that ‘Johnny Mac’ took some time off to recover from the pressure cooker that is the ATP circuit. As a hardcore fan of the Queens native I was guttered to see him do that but in retrospective it was understandable. McEnroe completed at the highest level in both the singles and doubles competitions and remains to this day the only player to hold the #1 ranking for both simultaneously in the Open Era (Stefan Edberg held #1 spot for each but never at the same time). He was arguably the most natural talent of his generation.

John McEnroe source: International Tennis Hall of Fame

However on deeper reflection Mac had probably lost his edge about a year earlier. 1984 was his greatest year as far as his all time performance was concerned. He won both Wimbledon and the US Open in straight sets but also surrendered a two set to love lead in the French Open to hand Ivan Lendl his first Grand Slam title. The defeat hit McEnroe harder than he may have believed at the time.

Lendl was transforming tennis into a game where athleticism was playing a bigger role and McEnroe’s style which relied on as great deal of personal flair and brilliant touches was looking to take more of a back seat. The Czech would hone this style starting in 1985 with McEnroe being pushed to play second fiddle. His loss in the US Open final of that year to Lendl was indicative of the passing of the guard and for the American who was for all intent of purposes the best player of the early 80s that was a tough blow. His enthusiasm waned and this was not helped by the arrival of Boris Becker and Stefan Edberg onto the scene.

Both could rival McEnroe on grass and each provided a new dynamism that was driven by superb conditioning. McEnroe would have to change his style of play.

The period he took off pushed him further behind as his age crept upwards and although he would still see semi-final Grand Slam success here and there, he struggled to adapt to a changing physical game that involved considerable base line running and power serving. The sport had moved on and had changed to favor a specific type of athlete of which Lendl was the prototype.

The reality is that McEnroe never worsened in the short run (in the long run age kicked in). What happened is that the ground chased beneath him and he could never fully adapt.