Gilles Muller using his time wisely

Brad Gilbert maximized every ounce of his ability on the tennis court. Most would say he overachieved in reaching the top five.

When he talked, Andre Agassi and Andy Roddick listened.

"One of the things in tennis you never want to do is look back 10 years after you're done and think, 'Geez, if only I would have done this and that differently,'" ESPN analyst Gilbert said. "I'd say making all the right decisions doesn't guarantee it's going to make you a better player, but it's sure as heck going to give you a better chance."

It took a while, but Gilles Muller has come to that realization.

Once a former junior No. 1, the 28-year-old left-hander with one of the most potent serves around -- who happens to hail from one of the smallest tennis-playing nations around, Luxembourg -- is trying to get the best of what remains of his career. He knew he needed to make adjustments to his lifestyle and game -- and did it.

Unprecedented success, for him, has followed. Dropping to outside 450th in the rankings last season, Muller surged to a career-high 42nd last month and is one of the tour's candidates for comeback player of the year. He's currently 45th, which means he probably won't have to play Challengers and worry about trying to qualify for events in 2012.

What a relief.

Muller can aim for loftier heights, like attempting to win a first title and reaching another Grand Slam quarterfinal. For the majority of his stint on tour, he has been known as a player who could sporadically pull off an upset, like beating Roddick at the U.S. Open, Agassi in Washington and Rafael Nadal at Wimbledon.

"As a kid I dreamed of playing in those big tournaments, and when I was there I took it for granted, which was a pretty bad mistake," Muller said. "Now I know how hard it is to get there and I don't want to just give it away. That's what I did when I was younger, give it away."

When speaking by phone from Moscow, where he was taking part in the Kremlin Cup in October, Muller's newfound lifestyle was evident.

He opted for room service from his hotel for dinner, but beef stroganoff, usually infused with cream, and meat dumplings weren't on the trolley.

"I got a salad," Muller said. "I'm trying to stay healthy. It's not always easy."

But it's easier than it was previously. He admitted that if he was hungry late at night, he'd have no problem eating pizza, one of his favorite foods. If he wanted to hang out with friends and return in the wee hours of the morning, he'd do that, too.

Muller was far from a party animal, but for a pro tennis player, more discipline is required.

"I would go for a drink with some friends," Muller said. "I would come back at midnight or 1 a.m. and would only have seven hours of sleep, then go to practice.

"It's complicated. You're still young and you have to sacrifice some things as a kid -- and you want to get that back."

Largely as a result, only once in his career has Muller managed to stay inside the top 100 in an entire season, 2005.

"Six-foot-four lefty, big serve, he smacks the groundstrokes, plays very aggressive," Gilbert said in a phone interview. "Not an easy out. A lot of times I would see his results, and he'd be losing in Challengers. His results would kind of perplex you. It's like, 'Why isn't this guy doing better?'"

A serious knee injury also contributed, and this was after Muller became more committed. He missed the final six months of 2009 because of patella issues in both knees. Despite venturing to the quarterfinals of the U.S. Open a year earlier, when he engineered a pair of two-set comebacks and tested Roger Federer, Muller saw his ranking plummet from 85th to 280th that September.

Doctors told him the injury could flare up at any time. To counter a reoccurrence, he lost weight to alleviate pressure on the knees and sees an acupuncturist.

"The doctors said the chance of it coming back is bigger than the chance of it not coming back," Muller said. "So far it hasn't. I'm hoping for the best."

Free of pain, Muller set himself a target of re-entering the top 100 in 2011. He got there in June and has kept on moving, the U.S. Open again proving pivotal.

Muller advanced to the fourth round in New York, falling to Nadal, a familiar foe. He stretched Nadal to tiebreakers in the first two sets at Wimbledon in June.

The good form continued in Metz, where Muller almost reached his first final in six years. He was undone in the semis by one of the circuit's most productive indoor performers, Ivan Ljubicic.

His game plan is simple: Get to the net as much, and as quickly, as possible. It's not simple to execute, given how well his peers return serves and hit balls from the baseline.

"Gilles is a little bit like Mardy Fish, not as good for the moment, but he's become more mature," Muller's former coach, Horacio Rearte, said in a phone interview. "He knows his body and he knows what he can do."

And he wants to do it for up to five more years.

"The first few years I didn't work too hard so I don't think I'll be tired at 30," Muller said. "Then I lost another year when I was injured, so I think I still have a lot of time."

Time he's using more wisely.

London-based Ravi Ubha covers soccer and tennis for ESPN.com. You can follow him on Twitter.