Andy Roddick probably should have skipped this year’s French Open. Nadia Petrova should have challenged for the title. Instead, they both booked their passage out of Paris yesterday after deflating first-round losses on a cold day at Roland Garros.

The highest-ranked American suffered another dismal defeat at the hands of a more experienced clay court player, though this time he could blame his demise on an injured ankle.

Roddick retired after falling behind 6-4, 7-5, 1-0, when a trainer said he could not reapply the tape on Roddick’s left ankle until the end of the third set. Considering that Alberto Martin, a 27-year-old Spaniard suffering through a disappointing season, had controlled the match to that point, there was no reason to soldier on.

“I don’t know if it was the scenario of being down two sets as opposed to being scared of a major injury,” Roddick said, referring to the ankle he rolled in Germany last week. “You roll it again, and who knows how long I’m out.”

Roddick has never advanced past the third round in Paris, and little was expected of him this year despite a favorable early draw (he had beaten Martin in their previous four matches, including one on clay).

While much has been made of how clay courts take some of the sting out of Roddick’s serve, the real problem is that he has suspect footwork and little understanding of how to move on clay. If Roddick ever slides on a groundstroke, it’s usually after his follow through, leaving him out of position.The sport’s most slippery surface puts those who do not train on it at a serious disadvantage. American tennis institutions need to address this soon, so the next Roddick is not so vulnerable in Paris.

Nevertheless, chances are Roddick would have beaten Martin were he at his best, and a win or two here might have relieved some of the frustration that has built up in first half of 2006. For most of the first two sets, he did not seem bothered by his injury, though he said later that it flared up in the first set and more so in the second when he tried to jump for an overhead at 5-5. Martin had hit one of several elegant topspin lobs, and this one floated over the grounded Roddick for a winner. Roddick double faulted on break point and then Martin served out the set.

“It was starting to affect the way I landed on my serve, “Roddick said. “And not much is working besides my serve. It was a lost cause, I think.”

In truth, Roddick’s serve is not living up to its reputation, either. In 26 matches tracked this year by the ATP Tour (excluding yesterday’s loss), Roddick won 87% of his service games, compared to 93% last season (in 73 matches). In 2003 and 2004, he won 91% of his service games. This year, his first-serve percentage is down 3% to 63%, and he is winning 78% of those points, compared to 82% last year. The decline has canceled out some improvement in his weak return game: 26% of return games won so far, compared to 21% last season. At least Wimbledon is around the corner.

While Roddick said he was perhaps “stupidly optimistic” when he arrived in Paris, Petrova had far greater expectations. After several years of failing to make the most of her immense physical gifts, the 23-year-old Russian had won more matches (33-7) than any woman this year, and had yet to lose on clay in 15 tries. In Berlin, she defeated Justine Henin-Hardenne, the defending French Open champion, in the final. It seemed that she had finally added mental fortitude to her arsenal.

Petrova missed the final clay-court tune-up in Rome with a pectoral injury that she said felt fine coming into Paris. On Saturday, though, she tweaked a muscle near her groin. She said the injury limited her movement yesterday in a listless 6-2, 6-2 loss to Japan’s Akiko Morigami,a 26-year-old who had a losing record this year (8-9). Morigami, ranked no. 69, had her best showing at a Grand Slam event in Paris last year, when she reached the third round.

One hesitates to attribute this loss to Petrova’s injury. She said it was not painful, but limited her movement; she played without a wrap on her leg. Even with an injury of this kind,Petrova ought to defeat a player like Morigami.Look no further than her more-heralded countrywoman, Maria Sharapova, whose ankle injury seems more severe than Petrova’s mysterious ailment. Sharapova is far less comfortable on clay, yet she saved three match points in the first round against Mashona Washington, whose skills are comparable to Morigami’s. If Petrova werea champion-in-waiting, she would at least have given Morigami a fight.

Petrova’s dismissal works in the favor of Henin-Hardenne, who won her opening match yesterday 6-3, 6-0 over Maret Ani of Estonia.Rather than facing Petrova in a potentially grueling quarterfinal, the Belgian should come up against a less imposing opponent.

***

Gael Monfils and Andy Murray are two 19-year-old up-and-comers who often looked lost yesterday in their ragged first-round match.The Scotsman Murray squandered an early lead in the first set, recovered to win sets two and three, and then played meekly after injuring his back, giving Monfils a 6-4, 6-7(2), 1-6, 6-2, 6-1 victory.

At this point, Murray is the more accomplished player and the lesser athlete (this was not his first bout with on-court injuries).He has quick hands,constructs points well, is competent at the net, and mixes slices and off-speed loops with more powerful strokes. Monfils’s game has less polish. He might win another round, but likely no more than that.

tperrotta@nysun.com