Jelena Jankovic underlined her threat to win the French Open on Friday by overpowering Venus Williams 6-4, 4-6, 6-1 in a high-quality third round tie.
The 22-year from Belgrade has been in impressive form this year winning three titles in Auckland, Charleston and most recently in Rome and she had beaten Williams on the last two occasions they had met.
First upon the centre-court and with the sun shining for once, Jankovic won the toss, chose to receive and the tactic paid off as the 25-year-old Williams served up a dreadful game.
Jankovic moved 2-0 before Williams started to find her range and the fourth-seeded Serb comfortably held on to her serve a further four times to take the set 6-4 in 30 minutes.
Williams came into the third round tie as a five-times Grand Slam title winner but she has never been too comfortable on the slow claycourts despite reaching the final in 2002 when she lost to sister Serena.
This time the American held her serve to open the second set and then attacking the Jankovic forehand paid dividends as she broke in the next game to take a 2-0 lead.
Williams, who hit the fastest women's serve ever in a Grand Slam event at 206 kilometres an hour in the previous round, had a chance to go 3-0, but Jankovic held firm and had the American gasping for breath after a punishing series of long rallies.
That paid dividends in the fifth game as the Serb broke back to get to 2-3, but Williams hit back immediately winning the next three games to move 5-2 up.
She failed to level the tie on her own serve but did so in the following game breaking Jankovic's serve for the third time in four goes.
But it was the Serb who proved the stronger in a pulsating final set breaking the Williams serve in the third and fifth games to move 4-1 up. That broke Williams's resistance and two games later it was all over.
Also into the last 16 early on was 29-year-old Tathiana Garbin of Italy who reached the fourth round of a Grand Slam event for the first time at her 28th attempt with a 6-3, 6-0 win over France's Stephanie Cohen-Aloro.
Both top seeds, Roger Federer and Justine Henin were scheduled to be in action on the sixth day of the tournament with the top half of both draws playing for places in the fourth round, final 16.
Federer, who has yet to drop a set, was going up against Italian clay-courter Potito Starace who took a set off the world No.1 on the surface at Gstaad in 2004.
Defending champion Henin was to follow taking on tall Italian Mara Santangelo, a player she has beaten four times out of four.
Also on the card were Serena Williams against Michaella Krajicek of the Netherlands and men's fourth seed Nikolay Davydenko of Russia facing the challenge of French hope Michael Llodra.