Third seed Amelie Mauresmo slumped out of the U.S. Open on Wednesday following a listless 6-4, 6-1 defeat by fellow Frenchwoman Mary Pierce in the quarter-finals.
Pierce took advantage of a nerve-riddled display from Mauresmo to reach the last four at Flushing Meadows for the first time.
She will next face either second seed Lindsay Davenport or Russian sixth seed Elena Dementieva.
"What can I say?" said the 12th seed.
"I am 30 and I have been on the tour for 17 years and there are still firsts for me. That's pretty amazing.
"I am just feeling so great. I am healthy and able to play out here in front of my fans. It's great."
Mauresmo, who has never won a grand slam title, looked tight from the start and allowed Pierce to surge into a 5-2 lead.
The third seed lifted her game a little to recover to 5-4, but then handed Pierce the set when she mis-hit a forehand wide.
Pierce, who was runner-up to Justine Henin-Hardenne at French Open in June but avenged that defeat in the previous round at the Open, picked up where she left off against the Belgian with some fine play.
Mauresmo also contributed to her own downfall with a succession of errors and double-faults, most of which came on important points.
Pierce broke to lead 2-0 and repeated the feat in the sixth game to clinch victory in 65 minutes.