The 12-time grand slam winner was stunned in the quarter-finals at Roland Garros by world number 72 Marco Cecchinato.
Italian Cecchinato won in four sets, scrambling over the line in an epic tie-break on his fourth match point.
Afterwards a dazed Djokovic, who has struggled with injury for much of the last year, was asked when he planned to make his first grass-court appearance.
He replied: “I don’t know. I don’t know if I’m going to play on grass. I don’t know. I don’t know what I’m going to do. I just came from the court. Sorry, guys, I can’t give you that answer. I cannot give you any answer.
“How do I regroup? I don’t know. I’m just not thinking about tennis at the moment.”
The Serbian needed lengthy treatment on a neck problem after dropping the first set.
But Cecchinato proved an even bigger pain in the neck for the 2016 Paris champion.
Djokovic had two set points at 6-5 in the second but went on to lose the tie-break.
Cecchinato was mixing things up to great effect, tying Djokovic to the baseline while throwing in regular, at times remarkable, spin-heavy drop-shots from the back of the court.
Yet Djokovic won the third set at a canter, and a suddenly frustrated Cecchinato was hit with a point penalty for unsportsmanlike conduct.
The storm seemed to have blown itself out and djokovic served for the fourth set at 5-3.
But from somewhere Cecchinato got a second wind, breaking back and forcing a tie-break.
It was a classic, Djokovic wasting three set points and Cecchinato unable to take the first of three for the match.
But on number four Djokovic left a looping backhand return which landed just in and Cecchinato celebrated a famous victory, 6-3 7-6 (7/4) 1-6 7/6 (13-11).
Cecchinato had not won a single grand slam match until he arrived at Roland Garros, but the 25-year-old is now the first Italian to reach the semi-final since Corrado Barazzutti 40 years ago.
He said: “Maybe I’m sleeping. It’s amazing. It’s unbelievable for me. For me to beat Djokovic in a quarter-final at Roland Garros it’s amazing.
“For me, it’s the first time semi-final grand slam. Now I need to think for the semi-final and I need some rest for recovery. I am very happy.”
— Roland-Garros (@rolandgarros) June 5, 2018
The 23-time Grand Slam champion revealed that she had suffered a pectoral muscle injury during her game against Julia Goerges.
“I unfortunately have been having some issues with my pec, my pec muscle, and (it) has unfortunately been getting worse to the point where right now I can’t actually serve. It’s kind of hard to play when I can’t physically serve,” Serena said.
The 36-year old did not answer whether she will compete at Wimbledon.
Serena Williams announces her withdrawal from #RG18 due to a right pectoral injury.
Wishing the three-time champion a speedy recovery. pic.twitter.com/bo3e1jkgcv
— Roland-Garros (@rolandgarros) June 4, 2018
“I’m beyond disappointed,” she said.
“I gave up so much time with my daughter and time with my family all for this moment. So it’s really difficult to be in this situation.”
Meanwhile, Sharapova said she was sad to see her opponent go out this way and wished her a quick recovery.
“I was looking forward to my match against Serena and am disappointed that she had to withdraw.”
“I wish her a speedy recovery and hope she returns to the tour soon.”
The 2016 Paris champion is still not at his dynamic best following a long absence due to an elbow problem, but he did not have to be to get past the 30th seed.
Djokovic took the first set, a slugfest of deuces which lasted almost an hour, with a solitary break of serve.
He repeated the trick in the second, taking eight points in a row on the way, but not without complaining to the umpire about the slippery court.
Meanwhile, Verdasco had slipped off a trainer to reveal toes heavily covered in plasters while receiving treatment for a blister on the sole of his foot.
The Spaniard grimaced his way through the third set as Djokovic broke twice to run out 6-3 6-4 6-2 winner.
Alexander Zverev has become marathon man of Roland Garros after coming through another five-setter to book his place in the quarter-final.
The 21-year-old German, seen along with Djokovic as one of the few obstacles to Rafael Nadal claiming an 11th title, was 2-1 down in sets for the third straight match, this time against Karen Khachanov.
But second seed Zverev roared back to oust the 6ft 6ins Russian, ranked 38 in the world, 4-6 7-6 (7/4) 2-6 6-3 6-3.
Despite his lofty seeding this is the first time Zverev had reached the last eight of a grand slam.
He has now played 18 sets to Nadal’s nine, with the Spaniard facing unseeded German Max Marterer on Monday in his fourth-round tie.
But Zverev insists he is more than happy to keep going the distance.
He said: “It’s about trying to find a way and trying to win. That’s what I am able to do in the last few matches, and I’m very happy about that.
“I’m very happy about being in the quarter-finals here going the hard way, going the long distance every single time and, you know, showing myself, showing everybody that I can play for as long as I need to.
“I’m in the quarter-finals of a grand slam. If you’re mentally fatigued, then something is wrong with you”
A 12th Roland-Garros quarterfinal for @DjokerNole.
— Roland-Garros (@rolandgarros) June 3, 2018
Provided by Press Association Sport