A year ago, Gilles Muller was a little-known player from Luxembourg plying his trade mostly in the tennis circuit's version of the minor leagues. Then in August, he pulled a shocking upset of Andre Agassi in the semifinals of the Legg Mason Tennis Classic and finished 2004 with his highest career ranking.

He returns this summer having made the transition to a full-time player on the ATP Tour more self-assured, with a higher profile and the challenge of meeting the expectations that come with it. Muller, the Legg Mason runner-up last year, advanced yesterday to the third round with a 7-6 (7-2), 6-4 victory over ninth-seeded Nicolas Massu.

Muller admits the past year has been a bit of a roller-coaster ride as he makes the adjustment to competing every week against top players. The 22-year-old struggled early, losing in the first round of his first three tournaments. But he turned the season around in June by reaching the third round of Wimbledon, and advanced to the final of a hard-court tournament in Los Angeles, where he fell to Agassi.

"It was quite tough," Muller said of competing in more ATP events. "The players are so much better. Sometimes, in the challenger tournaments, you might take for granted that you will play someone ranked so much lower than you in the first round. But now, you have to be there 100 percent in the first round. I had to get used to that. That's the big difference."

After not having played on hard courts since March, Muller arrived in Los Angeles last week and tore through the draw with victories over U.S. Open Series leader Robby Ginepri and Dominik Hrbaty. In the final, he failed to convert a set point in the second against Agassi to extend the match to a decisive third.

"I felt like if I had served better in that match, it might have been different," Muller said. "I was relying too much on second serves, and you can't do that against Andre. He puts so much pressure on you, and then I'm playing more defensive. Even though I lost the match, I feel like my tennis is getting better, and I can compete with the top players. I've gained a lot of confidence."

If Muller needs another gauge to see how far his tennis has come, he will get one today in his match against Arnaud Clement. The scrappy veteran Frenchman advanced with a 6-2, 4-6, 7-6 (9-7) victory over Richard Bloomfield. Clement has defeated Muller in two earlier meetings, the second of which was in 2004 at a hard-court event in France.

"He has a very good serve and a good backhand," Clement said of Muller. "And when he has time, his forehand is pretty good. He's just a very good all-around player. He does not have any weaknesses. I'm just happy to still be in the tournament. Tomorrow is another day, and we'll see."