Marat Safin's spring comeback on clay ended in a second round knockout at the Estoril Open Wednesday at the hands of fellow Russian Nikolay Davydenko.

More than two months after returning to tennis following a major knee injury, former world number one Safin is still puzzling over his lack of consistent form, evident in his 4-6, 6-1, 6-2 defeat to the second seed.

"How can I be satisfied after a score like that," lamented the 26-year-old who has US and Australian Open titles on his honours list.

"I couldn't find my game. Instead of attacking at the start of the second set, my game completely broke down. in the second round in six of his seven appearances.

Davydenko broke his duck in the series after losing twice within days to his compatriot in 2006.

Safin stepped back into the game in February at the expense of Davydenko, beating him in the first round of Dubai and following up just days later with a third-round victory at Indian Wells.

"In the second I played much better," said Davydenko, currently the world number six.

"My confidence is improving after losing my first three matches on clay. But I'm not thinking any farther than the next round."

Two other seeds made early exits, with unfancied American Justin Gimelstob producing the biggest shock.

The 29-year-old who before this week had last won an ATP-level match on clay in 1999, stunned Chile's seventh seeded Olympic champion Nicolas Massu 2-6, 7-6, 6-4.

Gimelstob, who travelled to European clay for only the second time in his career outside of three Roland Garros appearances, confessed that he was as surprised as anyone else.

"I came over with no expectations," said the American, who was eliminated at the first round in Barcelona

last week by Argentine Agustin Calleri.

"I don't know how much longer I have in my career. I wanted to try some new experiences and I'd heard good things about the spring circuit.

"I was killed last week in Barcelona. I was so bad last week. If I can win on clay, then anyone can.

"No one will believe when they read in the newspaper that I beat Massu.

"They'll think he broke his foot or something."

Gimelstob will on Friday face his doubles partner, Spanish specialist Albert Portas, whose career claim to fame so far is a surprise 2001 Hamburg masters crown.

"He's the heavy favourite, I'm like a bit of gum on his shoe, " said Gimelstob.

Gimelstob claimed his last clay success in Florida seven years ago in the first round when Delray beach, now hardcourt, was played on the surface.

Portas booked his place against his doubles partner with a knockout of French fourth seed Gael Monfils 3-6, 76, 6-4.

"I had chances and didn't take them and I had so many errors."

Safin said he has no choice but to keep plugging away with coach Peter Lundgren as Roland Garros draws closer.

"What other option is there," said the tortured Russian. "I have to play, practise and put in the work. Something just has to change."

Safin will continue onto Rome for next week's Masters, where he has lost