Jelena Jankovic slumped to the court, lay on her back for nearly a minute, then slowly rolled to her side. She eventually picked herself up and walked painfully to the net to shake hands with Tsvetana Pironkova.

Jankovic had won, but there was no joy in her gestures.

Cramping severely in an epic third set, the eighth-seeded Serb prevailed 4-6, 6-2, 7-4 over Pironkova, a 19-year-old qualifier from Bulgaria, to reach the quarter-final of the Porsche Grand Prix on Thursday.

Jankovic, a U.S. Open semifinalist, was overcome with cramps leading 4-2 in the third set with Pironkova serving at 30-30.

After receiving medical treatment, she returned to finish the game, which had started about 30 minutes before midnight. It was past midnight when it ended and Jankovic had gained another break of serve to lead 5-2.

It would take nearly another half-hour for her to close out the match, which lasted two hours and 35 minutes _ the third set alone took 75 minutes.

Earlier, fourth-seeded Russian Nadia Petrova cruised into the quarter-finals by beating Anna-Lena Groenefeld, the remaining German, 6-3, 6-4.

The US$650,000 indoor tournament lost top-ranked Amelie Mauresmo of France to a right-shoulder injury. She withdrew shortly before she was to play her first match against Michaella Krajicek of Netherlands in the second round.

American Lisa Raymond, who took Mauresmo's place in the draw as the highest-ranked loser in qualifying, lost 6-4, 6-2 to Krajicek, while Daniela Hantuchova of Slovakia upset sixth-seeded Dinara Safina of Russia 6-2, 6-2 and fifth-seeded Patty Schnyder of Switzerland outlasted Israel's Shahar Peer 7-6 (3), 2-6, 6-4.

Mauresmo said she didn't know if she would be able to play at the Kremlin Cup in Moscow next week.

Kim Clijsters, Justine Henin-Hardenne, Maria Sharapova, Lindsay Davenport, Serena and Venus Williams and Ana Ivanovic also pulled out of the tournament with injuries.

Mauresmo is seeking to finish the year as No. 1 in the world for the first time in her nine-year career.