A more improbable Wimbledon [Images] fourth-round contest you are unlikely ever to witness.

Andy Roddick [Images], beaten only by world number one Roger Federer [Images] on grass in the last two years, will play Guillermo Coria, an Argentine baseliner born to slide on clay, on Monday.

"Unbelievable," the 23-year-old Coria said after coming from two sets down to beat Austria's Jurgen Melzer in the third round on Saturday -- his second successive five-set thriller after despatching Xavier Malisse in the second round.

No wonder.

In three previous attempts to transfer his bewitching claycourt skills to the slick lawns of Wimbledon he has never gone beyond the second round.

"I'm not falling over like I used to do in my first years here, that makes me happiest," added Coria, once regarded as the world's best claycourt player until the emergence of Spanish teenager Rafael Nadal [Images] this year.

Bizarrely for a man who won 31 consecutive claycourt matches in 2004 before falling to Federer in the final of the Hamburg Masters, he has travelled as far at Wimbledon as he did earlier this month at Roland Garros.

"I've learned to believe that I, too, can be a dangerous player on grass," added Coria, who relies on converted cricket pitches for grasscourt practise back home in Argentina.

"I want to be a complete player This is the most difficult surface for me, but it's a big challenge for me to be able to play well here."

The challenge for the 2004 French Open runner-up does not come much bigger than fending off the world's fastest server on the world's fastest surface.

POWER SERVE

Roddick, the second seed and last year's runner-up, turned up the power on his deadly first serve to dangerous proportions on Saturday during his three-set defeat of Russian Igor Andreev.

In the opening set he surrendered just three points on serve, hitting the target with nearly 100 percent of his first deliveries.

After a year in which questions have been asked about Roddick's ability to stay at the top, the man with the 155 mph (249 kph) first serve is clearly enjoying being back on the slick lawns of the All England [Images] Club.

"You know, mission accomplished for the first week. Now it's time to get down to business," Roddick said ominously, as he looked ahead to Monday's fourth round.

"The players who really know how to play on [grass] really have an extreme advantage.

"If we had a three-month grasscourt season like the claycourt season, then maybe it would be a little different but I don't know."

Roddick has won all four encounters against Coria, the last being at the Tennis Masters Cup in Houston last year. Monday's meeting will be the first on grass.

"It's going to be a good match because it will show me where I am, what my level is on this type of surface," said Coria.

"I'd love to have him in front of me on a clay court. Unfortunately I have to play him on grass."

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