Younes El Aynaoui, the darling of men’s tennis last year and a crowd favorite wherever he plays, won’t be writing a story of comebacks, fist pumps, and between-the-legs winners at this year’s U.S. Open.

The “Rockin’ Moroccan,” as his fans call him, bowed out with an injury yesterday in what might have been a dynamite first-round match against Taylor Dent. El Aynaoui, who turns 33 in two weeks, has struggled with a right-foot injury all season and has played just four tournaments, including the Olympics. He seemed to roll his foot chasing down a Dent volley early in the first set, and from there had no lift in his legs and little pop in his serve. He defaulted down 6-1, 2-1.

“I thought that the foot was better,” El Aynaoui said in the locker room after his match, his foot encased in a bag of ice. “Then suddenly it came back again strong.”

El Aynaoui, a late bloomer who was not picked to succeed as a young player, played two memorable matches here last year, beating Jiri Novak in a fifth-set tiebreaker and then dispatching Carlos Moya to reach the quarterfinals. Earlier, at the 2003 Australian Open, he lost a spectacular battle with Andy Roddick, 21 games to 19 in the fifth set.

El Aynaoui’s followers packed the Grandstand yesterday to watch his unorthodox, go-for-broke tennis, but it was clear early on that, on this day, El Aynaoui had little to offer. Unfortunately, he may need ligament surgery, and doctors have warned him that it is a difficult procedure and could keep him off the tour for at least eight months. “I don’t want to really think about it,” he said.

Earlier in the day, top seed Roger Federer rolled to a 7-5, 6-2, 6-4 straight-set victory over Spain’s Albert Costa, who had beaten Federer in their last two meetings, most recently on clay in Rome.

If his match were a race, Federer would have been charged with a false start. He quickly lost his first service game, but he broke right back and stayed even with Costa, who eventually double-faulted on set point.

From there, Federer turned up the heat, bringing his serve up from the low hundreds to more than 130 mph to start the second set. He played fairly uneven tennis overall, but sprinkled in enough crisp volleys and forehand winners to overwhelm Costa, a clay court specialist who has had a disappointing season.

“I felt I had some very good moments attacking, good moments defending, and I’m also serving well,” Federer said. “It’s something I can build on for the next match.”

In what turned out to be the best match of the day, France’s Cyril Saulnier defeated hard-serving Greg Rusedski of Britain in five sets, 6-4, 3-6, 6-1, 3-6, 7-6 (9-7). Rusedski served and volleyed and attacked the net throughout, but Saulnier often found his range on the backhand side, ripping one-handed winners past his charging opponent. The two went at it for nearly three hours on a hot and humid day.

In his first match since coming home with a silver medal, American Mardy Fish made quick work of Spain’s David Ferrer, 7-5, 6-3, 6-2.