Djokovic earlier beat a hobbling Tomas Berdych of the Czech Republic, who retired with the score 6-7 (5), 6-2, 4-2.
The pair were evenly matched in the opening set with neither earning a break point in the first 11 games but Djokovic saved two set points before losing the tiebreak 7-5.
The Serbian second seed had looked sluggish in the first set but he offered more of a threat in the second, holding a break point for 2-0 and breaking for 3-1 when Berdych netted a backhand.
Both players saved break points in the next two games but Djokovic broke again for the set before Berdych called for the trainer and had his left thigh massaged.
Games went quickly in the final set as both players held serve comfortably until Djokovic broke to lead 4-3. Berdych lost the next two points before deciding to retire.
“The problem was my left quadriceps,” Berdych told reporters. “Was not able just to serve, move to the sides, and just feel the pain. It’s no chance to just play with this guy in the condition that I was feeling.
“Just didn’t make sense to be walking and just be able to finish, so that’s not my style. I felt it just too much for the serve and I couldn’t serve. So to play Novak, one of the best returners, this time to play without the serve, no chance.”
Djokovic was very unhappy with the way he played.
“I don’t know how to explain today’s match really. In one word, catastrophe,” the Australian Open champion said.
In Doha, top seeded Caroline Wozniacki stayed on course for her second straight title in the Gulf with a commanding 6-2, 6-0 win over Italian Flavia Pennetta in the quarterfinals of the WTA Qatar Open on Thursday.
Second seed Vera Zvonareva also advanced but not before she was taken the distance by marathon girl Daniela Hantuchova, who played her third consecutive three-setter of the tournament. Zvonareva won 7-5, 6-7 (5/7), 7-5.
The 20-year-old Danish superstar Wozniacki was clinical in her victory over the 15th-ranked Pennetta to set up a semifinal clash with Frenchwoman Marion Bartoli, who earlier in the day thrashed China’s Peng Shuai 6-2, 6-2.
The second semifinal will be played between Zvonareva and fifth seeded Jelena Jankovic, who overcame a knee injury to beat Czech Klara Zakopalova 6-2, 6-4.
Pennetta, who was playing in Qatar for the first time, began sensationally by breaking Wozniacki in the very first game of the match, but that proved the only bright spot for her as the Dane raised her level of play and breezed to victory.
Wozniacki now holds a 100 percent win record over Pennetta, triumphing in all their seven matches beginning at Bastad in 2009.
“I am very happy to make the semifinals,” said Wozniacki, who won the Dubai Open last week, adding that the fourth game when she broke back was the turning point of the match.
“I had to go for my shots in the game. That was the key,” added Wozniacki, who promptly put on a Liverpool jersey after the match to show her support for the club.
“I am a big Liverpool fan. I got this shirt today from the Qatar Tennis Federation. Liverpool are playing today (in the Europa League) so I thought I should wear it and show my support,” said Wozniacki who made just seven unforced errors.
Earlier, Bartoli completed a swift demolition job of Peng.
The world No. 18, who is unseeded in Qatar, hardly gave Peng a chance to find her footing in another hopelessly one-sided match to stay on course for a possible sixth title on the WTA Tour.
Bartoli, who had sent eighth seed Shahar Peer packing in the second round earning praise from the Israeli, was again ruthless, her trademark double-handed shots on either side often leaving her Chinese rival stranded.
She hit four aces and 22 winners, committing just nine unforced errors compared to Peng’s 18.
“I’m pleased with my level of play,” said the Frenchwoman. “I’m moving much better on the court compared to the previous years and I hope to continue playing like this.”
In Delray Beach, Florida, second-seeded Mardy Fish defeated Ricardo Mello 6-2, 6-1 in a matchup of former champions in the second round of the Delray Beach International Tennis Championships on Thursday.
The American advanced to the quarterfinals where he will play qualifier Alejandro Falla, who beat Adrian Mannarino 6-3, 6-2.
Juan Martin del Potro beat Teymuraz Gabashvili 6-1, 6-1
Del Potro will play fifth-seeded Kevin Anderson of South Africa in the quarterfinals. Anderson easily defeated Florent Serra of France 6-1 6-4.
The other quarterfinals feature sixth-seeded Janko Tipsarevic of Serbia against Ivan Dodig of Croatia, and 2008 Delray Beach champion Kei Nishikori against qualifier Ryan Sweeting.
The 16th-ranked Fish reached the Memphis semifinals last week and says he’s starting to feel better on the court after being diagnosed in November with a thyroid condition that can make him feel lethargic.
