LONDON - Novak Djokovic lay crumpled on Centre Court, clutching his upper left arm and grimacing. He felt something pop and feared the worst.
Djokovic had lunged for a shot behind the baseline, tumbled on the grass and rolled over twice, his racket flying from his hand. His new coach, Boris Becker, stood in the player's box and looked on gravely.
Slowly, Djokovic rose from the turf, still holding his arm across his chest and made his way to his chair.
"When I stood up, I felt that click or pop, whatever you call it," he said later. "I feared maybe it might be a dislocated shoulder or something like that."
After a medical timeout and treatment from a trainer, the top-seeded Djokovic needed just four more games to complete a 6-4, 6-2, 6-4 win over France's Gilles Simon on Friday, sending him into the fourth round and keeping alive his bid for a second Wimbledon title and seventh Grand Slam championship.
"Luckily there is nothing damaged," Djokovic said. "I just came from the doctor's office, ultrasound. It's all looking good. I'm quite confident that it will not affect my physical state or regimen or daily routine. I think it's going to be fine."
Djokovic will have two days off before an intriguing matchup Monday against another Frenchman, the free-swinging 14th-seeded Jo-Wilfried Tsonga.
"They told me usually in these kind of particular cases you might feel soreness in the next couple of days," Djokovic said. "But I can play around with practices and recovery and see how it goes. But I'm quite confident it's going to be all right for next one."
He felt all right enough to joke that he had talked to Becker about improving his style.
"We obviously need to work on my diving volleys, learning how to fall down on the court," he said. "I'm not very skillful in that."
Djokovic's injury scare came on a day that also featured the elimination of second-seeded woman Li Na and a three-set, 2 ½-hour Centre Court battle between two former female champions -- with 2011 winner Petra Kvitova overcoming five-time champ Venus Williams 5-7, 7-6 (2), 7-5.
Defending men's champion Andy Murray, who hasn't dropped a set this week, extended his winning streak at the All England Club to 16 matches by beating Roberto Bautista Agut of Spain 6-2, 6-3, 6-2. The streak goes back to his gold-medal run at the 2012 London Olympics, which was played at Wimbledon.
No. 6 Tomas Berdych, runner-up at Wimbledon four years ago, became the highest-seeded man to go out so far when he fell to No. 26 Marin Cilic 7-6 (5) 6-4, 7-6 (6) in match that finished in near darkness at 9:36 p.m. Berdych, who had called for play to be suspended because of the fading light, hit a forehand long on the second match point. Cilic finished with 20 aces.
Li, the Australian Open champion, fell 7-6 (5), 7-6 (5) to 43rd-ranked Barbora Zahlavova Strycova of the Czech Republic in the first major upset of the tournament. Since winning her second Grand Slam title in Melbourne in January, Li has lost in the first round of the French Open and now failed to reach the second week at Wimbledon.
Li double-faulted on match point -- after the point was replayed when she won a challenge on a forehand that had been called out.
Joining Kvitova and Zahlavova Strycova in the fourth round were two other Czechs, Lucie Safarova and Tereza Smitkova --the first time in the Open era four Czech women have reached the final 16 at a Grand Slam.
Kvitova beat Williams for the fourth time in five matches. All have gone to three sets.
Williams and Kvitova play similar games and they put on a Centre Court show of brutal power tennis. There were only three break points, and two breaks, the entire match. Williams came within two points of winning at 5-4 in the second set, with Kvitova serving at 15-30, but couldn't put her away.
Now 34, and slowed in recent years by an energy-sapping autoimmune disease, Williams made a strong showing at this tournament and again dismissed any talk of retirement.
"People have been trying to retire me since I was like 25," she said. "I'm not getting out of here. ... I'm finding my way back on my feet. I'm proud of myself for what I'm achieving on the court."
With seven major titles in her career, Williams hasn't given up on winning more.
"I want to win Grand Slams," she said. "Everybody does. No one gives it to you. They snatch it away and say, 'Mine.' That's what I'll have to do is snatch it, say, 'Mine,' too, growl if need be. "