Andy Murray showing grit in France

PARIS -- You don't have to play your best tennis to win, you just have to play better than your opponent. These three stars have had uncomfortable moments during this French Open but have competed hard and reached the second week. Now, each has a chance to do something special -- but must take care of business in their fourth-round matches first. How will they fare?

Andy Murray versus Viktor Troicki

Murray twisted his ankle in his previous match, but c'mon, he could have gotten through this draw on one leg. In the first three rounds, Murray played a qualifier ranked No. 124, a lucky loser ranked No. 126 and the world No. 95. Now he gets 15th seed Viktor Troicki, a tricky player but more dangerous on hard courts. He's someone Murray has comfortably defeated all three times they've played. Then it could be qualifier Alejandro Falla (who famously took Roger Federer to five sets at Wimbledon) or semi-solid clay-courter Juan Ignacio Chela for a spot in the semifinals. Not bad at all.

The only question is how the ankle will recover. Murray isn't sure. "I don't know if I'll be at 100 percent fit," Murray said. "Maybe I will be. You never know with these things."

So it's wait and see. But one thing that is sure is that Murray improved his level of play immensely after suffering the injury. Unable to move, he abandoned his usual rope-a-dope strategy, becoming as aggressive as everyone is always imploring him to be.

If the ankle is in reasonable shape and he maintains that level, he should get through Troicki just fine and could even make things interesting for Rafael Nadal or whoever he faces in the semifinals.

Troicki will at least be ready for the unexpected, having defeated the brilliant but erratic Alexandr Dolgopolov in the previous round.

Prediction: Murray in three

Rafael Nadal versus Ivan Ljubicic

If Nadal caught a tough break drawing giant server John Isner in the first round, he's been compensated by having easy pickings since -- an intimidated compatriot, Pablo Andujar, an overmatched qualifier, Antonio Veic, and now 32-year-old Ivan Ljubicic, who has been formidable on hard courts over his career. But he's less effective on clay and a serious underperformer at Grand Slams besides.

After a scratchy first couple of matches, Nadal looked better in his previous round, even if he sounded mentally weary afterward. Ljubicic is unlikely to win this match -- he might sneak a tiebreaker -- but the thoughtful, articulate Croatian veteran pinpointed exactly where Nadal is at the moment. "There is no question that his confidence is shaken," Ljubicic said. "You see him in the locker room. He's saying it. He's not hiding it.

"But we all know that the more tournament progresses, he's playing better tennis. So I don't think that I'm gonna be any more favorite or not favorite as much as I would be any other time on clay," he said.

"He's definitely still the man to beat on clay, I think. Obviously Djokovic, if the clash between them comes along, if they play the final, I think Novak will be slight favorite. But still, to beat Rafa on clay [in a] best-of-five; only one guy managed to do that in so many years, so there's no question that it's still very, very difficult to beat him."

Nadal would face a tougher test in the quarterfinals against in-form Frenchman Gilles Simon, a small but speedy and smart competitor who has troubled him in the past, or the big-hitting Robin Soderling, the only player to have beaten Nadal here.

Prediction: Nadal in three

Maria Sharapova versus Agnieszka Radwanska

Sharapova shouldn't even be here. She was almost down and out against 17-year-old French hopeful Caroline Garcia in the second round but somehow managed to turn it around. The match encapsulated both her strength and weakness at the moment. This is far from her best surface, but her experience and competitive steel make her stand out in a field that is extremely even and unpredictable. The swing factor could well be Sharapova's serve -- consistently strong when she won a big clay-court lead-up in Rome a couple of weeks ago. It was shaky in her first couple of matches here and then solid again in her previous match.

She will need it to work well against Radwanska, a canny player who can mix up play and move the ball around the court. Sharapova has won six of their seven meetings, but the loss was a big one -- coming at the 2007 U.S. Open when Sharapova was defending champion.

Sharapova will want to keep the points short and avoid getting into a running contest, which means the match would be won on her winners or lost on her errors. In good weather and fast conditions, she'll have the opportunity to do it.

A win against this kind of uncomfortable opponent would say a lot about Sharapova's chances to win the only Grand Slam she still lacks. Next up would be a match against friend Maria Kirilenko or Andrea Petkovic.

Prediction: Radwanska in three

Kamakshi Tandon is a freelance tennis writer for ESPN.com.