BEIJING (AP) Novak Djokovic and Andy Murray set up a semifinal at the China Open with convincing wins on Friday over two members of the younger generation enjoying breakthrough seasons.
The top-seeded Djokovic defeated Wimbledon semifinalist Grigor Dimitrov of Bulgaria 6-2, 6-4, while sixth-seeded Murray took out U.S. Open champion Marin Cilic 6-1, 6-4.
On the women's side, Serena Williams withdrew before her quarterfinal against Samantha Stosur with a left knee injury that raised doubts about her ability to play the WTA Finals in Singapore this month.
Third-seeded Petra Kvitova and fourth-seeded Maria Sharapova both won to make the semifinals.
Djokovic said that while younger players like Cilic, Dimitrov, U.S. Open finalist Kei Nishikori and Wimbledon semifinalist Milos Raonic are improving quickly and challenging at the majors, he believes it will still be a while before there's a changing of the guard in men's tennis.
His patience and experience showed against the fifth-seeded Dimitrov, who broke Djokovic twice in the second set but was unable to build on the momentum, making costly errors to give the breaks right back.
''It's logical to expect that in the sport, after so many years of dominance by three, four players, there are some others who are coming up,'' Djokovic said. ''But on the other hand, it's still not happening that they are the ones who are winning Grand Slams and being top three, four in the world.
''It takes time. How long? I don't know. I'll make sure that they don't come any time soon.''
Murray is enjoying his best stretch since back surgery last autumn and missing several months of the season. He lost a close four-set match to Djokovic at the U.S. Open and captured his first title since his 2013 Wimbledon triumph last week in Shenzhen.
He's hoping to carry that momentum into Saturday against Djokovic, who holds a 13-8 advantage in their series.
''It will be very good for me to get that match and see if I can make some improvements from the U.S. Open,'' Murray said. ''If I play like I did at the U.S. Open, I'll definitely give myself an opportunity.''
While there have been few surprises in the men's draw, the women's side has been hit hard by injuries. Defending champion Williams was joined on the sidelines by second-seeded Simona Halep, who withdrew from her quarterfinal against Ana Ivanovic on Thursday with a hip injury.
Williams said the pain was so bad in her three-set win over Lucie Safarova on Thursday, she had no choice but to pull out.
''It throbs just sitting, standing,'' she said. ''I felt it mostly serving because I'm landing on my left knee. That was really killer for me.''
She said she will go to Europe for a knee exam to determine the extent of the injury, and whether she can play the WTA Finals.
''If I feel this way for Singapore, I don't think it's smart for me to play,'' she said. ''I'm just going to see how it goes.''
Kvitova said after her 7-6 (2), 6-4 win over Italian Roberta Vinci that she was not surprised the long season was taking a toll.
''It's really difficult. I mean, I'm not feeling full of energy. I'm tired,'' she said. ''It's tough to find energy in the locker room.''
The two-time Wimbledon champion is on a roll, however, coming off a title last week at the Wuhan Open. She plays Stosur in the semis for a chance to reach her fourth final of the season.
Sharapova, a 6-0, 6-4 winner over fellow Russian Svetlana Kuznetsova, faces Ivanovic in a rematch of their tight three-setter at Cincinnati, where Sharapova lost after holding match point.
''It was a tough one to lose,'' she said. ''I always look forward to our matches. They're always very competitive.''