MONTREAL — Jelena Jankovic was upset by 19-year-old Dominika Cibulkova 7-5, 6-2 today at the Rogers Cup, losing yet another opportunity to claim the top ranking.

Jankovic could have claimed the No. 1 spot from Ana Ivanovic if she had reached the final. It was her fourth such chance this year, but she has lost each time — the other losses coming in the semifinals at the French Open, the round of 16 at Wimbledon and the semifinals last week in Carson, Calif.

"At the moment I don't deserve that spot," Jankovic said. "I am not in the best shape, I am not at my highest level. So it will take time for me to get better.

"The No. 1 spot doesn't matter," she said. "I want to be healthy, I want to improve, I want to play tennis. I don't really think about No. 1 or whatever happens. If it's going to happen, it will happen."

Jankovic took a 5-1 lead before the momentum shifted to Cibulkova. She reeled off six straight games — winning 25 of 34 points — and clinched the set with an ace. Jankovic said she became exhausted and dizzy after the first six games of the match.

"That's part of my game," Cibulkova said, "to make my opponents all tired, and then just beat them.

"I didn't start well," said Cibulkova, who will face 10th-seeded Marian Bartoli in the semifinals. "But I kept believing in myself and I knew that if I didn't make as many mistakes, I could get back in the match."

She took a 2-0 lead in the second set before Jankovic fought back to 3-2. Cibulkova won the final three games, clinching the match when Jankovic returned a second serve into the net.

Cibulkova knocked out her third seeded player of the week, including fifth-seeded Elena Dementieva and 12th-seed Nadia Petrova. She was ranked 156th in the world at the end of 2006, but was No. 31 coming into this event and now will go much higher.

"I'm just starting to feel more confidence in myself," Cibulkova said. "I'm starting to believe that I can beat the best players in the world. I'm not giving them as much respect."