Costa outguns Robredo

"I'm playing at a great level and why not repeat if I can hold on physically", Costa said.

For the fourth time in five matches at Roland Garros the defending champion triumphed in five sets to go through to a last-four clash with either third seed Juan Carlos Ferrero of Spain or Chile's Fernando Gonzalez.

"This the first time I play 4 five set matches in the same tournament, I'm amazed at myself for being able to keep up physically and mentally" he added.

Robredo, ranked 31 in the world and playing his first grand slam quarter-final, had beaten world number one Lleyton Hewitt and three-time former winner Gustavo Kuerten of Brazil on his way to the last eight.

A rampant Costa showed once more what he came to do on the red Parisian clay courts. However it was an uphill battle for the Spaniard, who had to lose the first two sets before beginning his charge.

"The only thing I try to do is continue and think I still have a chance", he said after the match. "I felt great physically and that's why I was able to win such an important match".

Facing Costa for the first time in his career, he raced into a two sets to love lead with some sublime claycourt tennis.

The match began with Robredo dominating Costa in every single department. The youngster rapidly took a 3-0 lead pounding Costa with his speed. He took the initiative in every point placing his shots well forcing Costa to be on the defensive every time.

Robredo punished Costa on his second ball producing thunderous returns leaving Costa helpless. The defending champion broke Robredo but the youngster quickly let Costa know who was in control romping to a 5-1 lead.

Costa tried many variations in his game to stop Robredo's attack and lower his confidence but his efforts were useless. Robredo wrapped up the first set with a blistering forehand in 36 minutes of play.

The second set was a tighter affair with Robredo achieving a late break in the seventh game to go up 4-3. He continued to overwhelm Costa with stunning forehands that kept pulling off winner after winner. Robredo changed gears and won his fourth consecutive game of the set breaking Costa to wrap up the set.

But Costa was no ready to give in powering his way through the third set finding his wind and breaking Robredo to serve for the set at 5-4. Robredo, visibly tiring and beginning to lose his temper, stumbled gifting Costa with a love game to wrap up the set.

Costa's return was evident as the defending champion continued to raise his level of game hitting more winners controlling Robredo's forehand pushing him behind the baseline.

Robredo lost his concentration following a bad line call from the chair umpire in the fourth game. From then on Robredo began to accumulate unforced errors gifting Costa with the break to go up 4

At 5-4 Costa was serving for the set but Robredo halted his charge levelling the score. However, Costa dug deep and broke back to then serve and level the match to two sets all for the fourth time in the tournament.

After three gruelling hours of play, the decider saw an invigorated Costa crush Robredo's game breaking the youngster twice to serve for the match. Costa built a barrage of brutal back-court blows burying his increasingly frustrated 21-year-old opponent after three hours 28 minutes.

Costa has spent 18-1/2 hours on court so far in defence of his only grand slam title.

He beat Argentine Sergio Roitman, Radek Stepanek of the Czech Republic and Ecuador's Nicolas Lapentti over five sets in rounds one, two and three before enjoying a brief respite with a straight sets win over France's Arnaud Clement in the last 16.