Despite a series of unforced errors, Federer took advantage of two match interruptions caused by rain to improve his game and beat Portuguese player Frederico Gil 6-4 6-1 under the gaze of his new coach and clay expert Jose Higueras.

"Gil played an excellent set-and-a-half," said Federer. "Thank God I could use the rain delays to improve my level of play."

The 26-year-old Swiss will meet unseededDenis Gremelmayr of Germany on Saturday after he beat Czech Jiri Vanek 6-2 3-6 6-2.

A visibly irritated and tired Davydenkostruggled to overcome FrenchmanMarcGicquel's powerful baseline game 6-4 5-7 6-3 in a gruelling two-and-a-half-hour match.

"I was tired and really nervous because of the weather," said Davydenko, the world number four and a winner in Estoril in 2003.

"Every point that I missed, every easy mistake, I was feeling more crazy - but I was fighting until the end and I won the match."

The Russian said his mental strength helped him overcome his exhaustion and the adverse weather conditions.

"I think it's the biggest strength I have," said Davydenko, who won the Miami title two weeks against over world number two Rafael Nadal.

He will face another Frenchman, Florent Serra, in Saturday's other semi-final. Serra defeated Italian Flavio Cipolla 6-1 6-1 in the last eight.