Novak Djokovic and fellow Serbian and Davis Cup teammate Janko Tipsarevic squared off in a physical quarterfinal match, splitting a set a piece, both of which were tie-breaks. But after the world No. 1 won the third set 6-0 and then took a 3-0 lead in the fourth set, Tipsarevic retired due to an injury in his leg. With the 7-6(2), 6-7(4), 6-0, 3-0 win, Djokovic earned a berth into the semifinals.

“Physically, unfortunately, he couldn't hold on,” Djokovic said after the match. “You could see that he could not move as well as he did in two and a half hours. I support anything he does because he's my friend and I know him well, and I know he's somebody who doesn't like to retire.”

It was an exciting first set that took one hour and 24 minutes to complete, with the 20th seed Tipsarevic and Djokovic exchanging several service breaks, two of which came at opportune times to save the set for each player. Eventually, the set went to a tie-break, and Djokovic played lights-out tennis taking out Tipsarevic 7-2.

The second set was much of the same, with both players exchanging breaks and sending the set into a tie-break. But this time it was Tipsarevic who came up with the win, 7-4.

Djokovic came out in the third set looking very strong and focused, breaking Tipsarevic three times and blanking him 6-0.

In the fourth set, Tipsarevic came out swinging, putting Djokovic on the defensive by taking a 0-30 lead on Djokovic’s serve. On the following point, after an extremely long rally, Djokovic hustled to return a volley and nearly did a split on the court to get the ball back for a winner. The crowd cheered and even Tipsarevic clapped for the performance. But the slide on the hard court hurt Djokovic’s foot and he had to take a medical time out to get his toe wrapped.

It was apparent as the set continued that it wasn’t Djokovic who was injured, but Tipsarevic, who had to get his leg wrapped earlier in the match. After Djokovic went up 3-0 in the fourth set, Tipsarevic opted to retire after playing three hours and 45 minutes.

The two players, who have played in doubles matches together and are frequent hitting partners and friends shared a long, shared a friendly hug at the net.

“Well, it's big because you don't get too often to see two Serbian players playing against each other in the last eight of one of the four biggest events in our sport,” Djokovic said about the importance of his match against Tipsarevic to his country. “So, yeah, it was exciting to play him and definitely to be a part of a great match. He can be proud with his performance, even though he had to retire.”

Djokovic will face either Roger Federer or Jo-Wilifried Tsonga in the semifinals.