Safina needed two chances to serve out the match against Clijsters
World number one Dinara Safina brought an end to Kim Clijsters' remarkable run in Cincinnati with victory in their quarter-final.
The Russian survived an onslaught from the Belgian, coming back from a break down in both sets for a 6-2 7-5 win.
Clijsters, 26, was playing her first event after a two-year break during which she gave birth to a daughter.
Safina goes on to face Flavia Pennetta, who beat Daniela Hantuchova 6-3 6-3 for her 15th straight consecutive win.
Italian Pennetta is the form woman on tour having won back-to-back titles in Palermo and Los Angeles, and seen off third seed Venus Williams already this week in Cincinnati.
Fourth seed Elena Dementieva defeated Caroline Wozniacki 6-2 6-1 to set up a semi-final against fifth seed Jelena Jankovic, who saw off Sybille Bammer 6-0 6-3.
I really felt Dinara played some of the best tennis I've seen of her
Clijsters, who had her first child in February of last year, had beaten French Open champion Svetlana Kuznetsova in the previous round and started well again.
She broke immediately and moved 2-0 ahead with some fearless hitting but Safina found her range and reeled off six consecutive games to take the set.
On another scorching day in Cincinnati, Clijsters took control again at the start of the second set and fashioned a 4-1 lead, only to see Safina recover with four straight games.
The home crowd, who were very much on the Belgian's side, were given a lift when Clijsters broke serve to stay in the match but Safina responded immediately and served out at the second time of asking.
"I really felt Dinara played some of the best tennis I've seen of her," said Clijsters. "She doesn't give you the opportunity to step in and put the pressure on her.
"She hits the ball extremely deep and down the middle of the court. It's a very good game plan she's developed in the last few years.
"I kind of feel like I want to go out there right now and do it all over again and try to figure out a few things. But overall I'm very happy and satisfied with the way that everything has been."
Safina said: "Overall I just played a very solid game. It was hard hitting from my side.
"I knew exactly what to expect from her because I took her like she was a top-10 player. She's one of the best players. I think I stayed very aggressive today and didn't let her dictate too much."