Kim Clijsters's brilliant comeback after two years off the tour came to an end at the Cincinnati Open on Friday when she lost 6-2, 7-5 to world number one Dinara Safina in the quarter-finals.
Former world number one Clijsters led 2-0 in the first set and 4-1 in the second but could not press home the advantage as Russian Safina powered her way into the last four.
"I really felt like Dinara today played some of her best tennis that I've seen of her," Clijsters, who gave birth to her first child last year, told reporters.
"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 that she's developed in the last few years. Obviously it's worked."
The Belgian 26-year-old, unseeded here and without a world ranking, launched her "second career" by beating Marion Bartoli, Patty Schnyder and French Open champion Svetlana Kuznetsova on the way to the quarter-finals.
"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 out there," she said.
"But overall I'm very happy and satisfied with the way that everything has been and with my level."
After Clijsters took an early break, Safina found her range and reeled off six consecutive games to take the opening set, only for the Belgian to storm ahead 4-1 in the second.
Again, Safina hit back and though she was broken when serving for the match at 5-4, she made no mistake second time round and served out for victory.
"I think overall, I just played a very solid, heavy game. It was hard hitting from my side," Safina said.
"I knew exactly what to expect from her because I took her like she is a top 10 player. For me, she's one of the best players. I think I stayed very aggressive today and didn't let her dictate too much."
In the semi-finals, Safina will meet Italian 14th seed Flavia Pennetta of Italy, who beat unseeded Slovak Daniela Hantuchova 6-3, 6-3.
The win was Pennetta's 15th consecutive victory, ensuring she will become the first Italian woman ever to be ranked in the top 10 when the new list is released on Monday.
Earlier, fourth seed Elena Dementieva cruised into the last four with a 6-2, 6-1 win over eighth-seeded Dane Caroline Wozniacki.
Wozniacki had beaten Dementieva twice this year but the Russian was rock solid as she set up a meeting with fifth seed Jelena Jankovic, who hammered unseeded Austrian Sybille Bammer 6-0, 6-3 in the night match.
"I am just satisfied the way I was playing the whole match," Dementieva said.
"I think the tactic for today's match was different for me. I was trying to stay aggressive and not play backhand crosscourt all the time, trying to mix it up, and it really worked."