Second seed Arantxa Sanchez-Vicario was sent crashing out of the Italian Open yesterday, the Spaniard upset by unseeded Austrian Sylvia Plischke 6-4, 6-1.

There was a fright too for French fourth seed Mary Pierce, who had to come back from match point to beat 15th seeded Spaniard Conchita Martinez 4-6, 6-0, 7-6 (7/2).

But American Serena Williams cruised into the last eight with a 62, 6-3 win over Romanian Irina Spirlea and is now seeded to meet world number one Martina Hingis for a place in the semis.

Sanchez-Vicario, who won last year's French Open for the third time, was her own worst enemy in an error-riddled third round performance against a player ranked 38th in the world.

Plischke kept attacking her opponent and was rewarded for her efforts with a quarter-final against either Switzerland's Patty Schnyder or Frenchwoman Amelie Mauresmo.

"I feel good on the court and I'm enjoying it," said Plischke, who on Wednesday dumped out South African 12th seed Amanda Coetzer.

"I had the feeling I played better yesterday," she claimed. "Arantxa wasn't on the greatest form, but I knew that I had to stay aggressive and not just wait for her to make mistakes."

Sanchez-Vicario knew what went wrong. "Yesterday I played well, but today I made too many errors," she said. "I think we both had many possibilities to win, but I didn't play very well. She played at her level, but I lost the match."

Plischke was joined in the last eight by Pierce, but only after a narrow victory over Martinez, a four-times winner, in nearly three hours.

Both women are powerful baseline players, and although Pierce's game had a better mixture of strokes, the match swayed according to who was able to avoid more unforced errors.

Pierce was able to break for a 31 advantage in the final set, and it ought to have been the turning point.

Instead, Pierce found herself 40-0 down on her own serve. She came back to deuce with an ace and had game point for 4-1 before being broken with a long forehand.

She also botched the 11th game to trail 6-5, and give Martinez the chance to serve out for victory.

However, Martinez missed a match-point at 40-30 with a backhand return which went wide and then flung her racquet down in fury as she was broken by a feeble forehand into the net, forcing the fatal tie-break.

Pierce, who is seeded to meet eighth seeded compatriot Sandrine Testud, couldn't remember the last time she won after coming back from match-point.

Meanwhile, Tim Henman displayed his growing confidence on clay by sweeping into the German Open quarter-finals in Hamburg yesterday. The British number one beat Argentinian Mariano Puerta 6-4 6-1, his second consecutive straight sets win on his least favourite surface.

And such is his new self-belief that the man who only last week ruled out his French Open chances now insists: "If I can play in these conditions, I can play anywhere."

Henman went a break down in the first set after losing the sixth game, but hit back with two successive breaks to take the initiative.

He swept through the second set as his 20-year-old opponent tired, Henman completing the victory in one hour 16 minutes.