Third seed Carlos Moya became the latest high-profile casualty at the Rome Masters on Thursday when he lost 6-4 7-6 in the third-round to Yevgeny Kafelnikov.
Moya followed world No. 1 Andre Agassi and fifth seed Andy Roddick in making an early exit from the competition.
Another Spaniard -- the reigning French Open champion Albert Costa -- also slipped up 7-5 4-6 6-1 to compatriot Felix Mantilla, but second seed Juan Carlos Ferrero ensured Spain had two representatives in the quarter-finals by beating Argentina's Gaston Gaudio 5-7 6-0 6-2.
Fourth-seeded Swiss Roger Federer played his best tennis of the week in overwhelming Spaniard Tommy Robredo 6-1 6-1, while Australian Open finalist Rainer Schuettler of Germany defeated eighth-seeded Czech Jiri Novak 6-4 7-6.
Moya -- French Open champion in 1998 -- began his match with Kafelnikov as favorite, having won 21 out of 23 matches on clay this year as well as two titles in Buenos Aires and Barcelona.
But the unseeded Russian picked up the pace of his groundstrokes in the 10th game to break serve and take the opening set.
Twice in a topsy-turvy second set the Spaniard came back from a break down to level the scores at 6-6.
Having battled back from a 3-0 deficit in the tiebreak to go 4-3 up, however, Moya then committed three unforced errors to gift two match points to his opponent.
Kafelnikov seized the opportunity, striking a backhand crosscourt winner to advance to the quarter-finals for the first time in 11 visits to Rome.
While Moya could not explain his sudden loss of form, Kafelnikov -- who held the world No. 1 spot in 1999 and triumphed at Roland Garros two years before the Spaniard -- attributed his renewed appetite and success to a decision to have surgery to remove painful varicose veins last December.
"Now at least I'm winning matches on clay where in previous years I wasn't able to do that.," he said.
Kafelnikov's reward is a quarter-final showdown against big-serving Dutchman Martin Verkerk, who gunned down Roddick in three tight sets on Wednesday, but had fewer problems disposing of his third-round opponent, Finn Jarkko Nieminen, 6-0 6-3.
Ferrero took more than two and a half hours to put down
Gaudio but denied his efforts would effect his form in the last-eight showdown with Schuettler.
"If I can come back into a match after a tough 75-minute first set like that, then I really must be in good shape," he commented after the match.
Federer's master class against Robredo was by far the most impressive performance of the day.
The Swiss, who has won three tournaments already this year, dispatched the claycourt expert with clinical ease, dominating the back of the court with heavy groundstrokes, crowding the net and never allowing his opponent to find range or rhythm on his shots.
Victory extended his recent record on clay to eight successive wins without dropping a set and sent the clearest warning yet to the baseliners left in the draw that pace and consistency alone might not be enough to stop him.