Novak Djokovic has crashed out the French Open
Djokovic lost in straights to Dominic Thiem today – the last set in which he was bagelled.
It's the first time Djokovic has lost a set to love at a Grand Slam since the US Open in 2005.
Tanking is the tennis term when players deliberately choose not to focus energy or attention on a specific set.
While commentating on the game on Eurosport, McEnroe said: “It looks right now as if Djokovic doesn't want to be on the court. This is tank city.
“I’m very surprised – especially with the way how it ended. That last set was really strange.”
Djokovic squandered two set points in the opening set and went on to lose 7-6 6-3 6-0.
His error-strewn display shocked Greg Rusedski too, who was appearing in the Eurosport studio.
He said: “When have you seen Djokovic lose 6-0 in a Grand Slam quarter-final? There are question marks for me are over where’s Novak – especially after that performance.”
- French Open 2017 Day 11 results LIVE: Djokovic, Nadal and Murray play
- Novak Djokovic OUT of French Open as Dominic Thiem wins
French Open prize money Fri, May 26, 2017
How much are players set to win at this year's French Open? As with all the Majors, men and women earn equal prize money at Roland Garros
Play slideshow AFP/Getty Images 1 of 8
This is tank city
John McEnroe on Novak Djokovic
Djokovic looked a shadow of the player who won at Roland Garros 12 months ago to become the first man since 1969 to hold all four grand slam titles at the same time.
The Serbian virtually gave up in the third set in what was a shocking end to his title defence.
The result was all the more remarkable given Thiem won just a single game the last time they met at the Italian Open in Rome three weeks ago.
He had only won one set in all their five previous meetings and lost easily to Djokovic here in the last four 12 months ago.
But that was a very different Djokovic. Even if it was clear something was still missing during his earlier rounds, no one would have expected the match to go quite like this.
Djokovic led 4-2 in what was a brutally physical first set lasting 73 minutes but played a poor game to hand Thiem the break back, serving two double faults.
Dominic Thiem downed Novak Djokovic in the French Open quarter-finals
Djokovic then had two chances to take the set at 15-40 on Thiem's serve in the 10th game but the 23-year-old saved them both in convincing fashion.
Conditions were cool and windy, with the court playing slow, but Djokovic could not blame that for the three awful backhands he played to give away the tie-break.
It was another sign that the Serbian is still searching for the mental and physical resilience that made him such an immovable force.
Thiem was showing all his considerable skills, flashing backhand winners down the line and punishing Djokovic with his heavy forehand.
He quickly moved 3-0 ahead in the second set and, although Djokovic initially showed some fight, it soon drained away.