Argentine seventh seed Guillermo Coria failed to make the same impression on grass that he has on clay this season, beaten 7-5, 7-6, 6-3 by Olivier Rochus in the first round at Wimbledon.

The 21-year-old Coria, who won the Hamburg Masters in May before knocking Andre Agassi out at the quarter-final stage of the French Open, fought hard but could not match the greater grasscourt experience of the Belgian.

Coria's hopes were raised after the second set went to a tiebreak, but when Rochus won it 7-4 the somewhat demoralised Argentine could not get a foothold in the final set.

The Argentine said that although defeat on grass was not unexpected, he was angry at himself for going out in the first round.

"I knew that it would be like that as I only had three days preparation," he told reporters.

"After Roland Garros I was too relaxed; I went back to Argentina and did not concentrate, but now I have to focus on the next tournaments."

The 22-year-old Rochus, who last year reached the third round, will play either Briton Richard Bloomfield or France's Anthony Dupuis in the second round.

In another upset of sorts, 2002 semi-finalist Xavier Malisse, seeded 14th, lost to Cyril Saulnier 6-4, 6-3, 6-2.

But David Nalbandian, an unheralded finalist at Wimbledon last year, eased his way into the second round with a workmanlike 7-5, 6-4, 6-2 victory over chunky Belarussian baseliner Vladimir Voltchkov.

The Argentine, facing much greater pressure this year as number six seed, said after his two-hour clash: "The first match is always difficult and it is good to get this one out of the way."

Voltchkov, another Wimbledon surprise package when reaching the semi-finals three years ago as a qualifier, could never maintain any pressure against the much steadier Nalbandian.

After a patchy start, Nalbandian attacked at just the right moment in the first set, breaking Voltchkov in the 11th game and then serving out for a 1-0 lead.

Nalbandian's solid baseline game moved up a gear in the second set and in the third, the resistance of a dispirited Voltchkov crumbled.

Solid start by Serena

Meanwhile, Serena Williams opened her Wimbledon defence with a solid if not overly impressive 6-3, 6-3 first-round win over fellow American Jill Craybas.

Striding on to court 24 hours after men's champion Lleyton Hewitt had been humbled on the same stage, a steely-eyed Williams took in her surroundings as she unveiled her rather understated orange-trimmed white outfit.

Determined to avoid the fate of Hewitt, Williams often paid the price for putting too much power behind her shots.

With a gentle breeze floating over the sun-drenched Centre Court, Williams tried to blast her 67th-ranked opponent off the court but instead saw the ball fall wide time and again.

Despite claiming three games in the opening set, the 28-year-old Craybas managed to hit only one winner -- a backhand volley in the sixth game.

With only 10 wins all season, Craybas simply lacked the expertise to conjure up the winners and netted an easy backhand to lose the first set in 24 minutes.

Playing her first match since her bitter defeat to Justin Henin-Hardenne in the French Open semi-finals earlier this month, Williams was again her worst enemy in the second.

Distracted by a broken string on her racket midway through the fourth game, she allowed her opponent to break back and level for 2-2.

That, however, was the last time Craybas was to draw loud applause from the crowd. From then on, Williams charged ahead and wrapped up victory with the loss of only one more game.

Williams will next face Belgian Els Callens for a place in the third round.

Dokic struggles

Jelena Dokic stuttered to an unconvincing 6-3, 1-6, 6-4 win over British qualifier Elena Baltacha to reach the second round.

The 20-year-old Yugoslav, seeded 11, had looked like playing out a routine first-round warm-up in bright sunshine on court 13, taking the first set in 39 minutes.

But she lost her way completely in the second set, spraying her normally penetrating groundstrokes wide, dropping her shoulders and scowling.

Dokic, who was brought up in Australia but reverted to Yugoslav citizenship after falling out with Australian tennis officials and media, has had a rough year on court.

She declined to play at the Australian Open, lost in the second round of the French and has looked out-of-sorts in all but a couple of tournaments.

She has stopped travelling with her controversial and outspoken father, who formerly coached her.

But she enjoys playing on grass and reached the semi-finals here in 2000, after famously ousting top seed Martina Hingis in the first round a year earlier.

This year's Wimbledon warm-up did not go well, however, and she lost in the first round of the Eastbourne tournament last week to Japanese qualifer Saori Obata.

"I'm just not playing well," she said after that match. "If I knew how to fix it I would."

Against Baltacha she did produce some fine serves and searing forehands and had to contend with a fiercely partisan crowd and an opponent, who though ranked 149 in the world, was thoroughly determined after reaching the third round here last year.

Dokic's performance was patchy though. She surrendered the 27-minute second set with a limp forehand into the net after thumping her racket in frustration.

She also produced nine double faults in the match which went with serve in the final set until, looking a little more like the world's 12th-ranked player, she broke Baltacha's serve in the last game, converting her first match point.