PARIS - Novak Djokovic's perfect season is still intact, and his clay-court form still looks devastating after he reached the third round of the French Open when Victor Hanescu retired Wednesday because of injury.

The second-seeded Serb, who joined 2009 champion Roger Federer in the third round at Roland Garros, improved to 39-0 in 2011 after Hanescu retired while trailing, 6-4, 6-1, 2-3. Djokovic has won 41 straight matches since last year's Davis Cup final.

"I keep on thinking only about the winning. I'm taking one match at a time," Djokovic said. "Really, I'm not thinking about when this streak - this amazing streak - will end. So I guess that's the right mental approach."

If he makes the final, Djokovic will be assured of the No. 1 ranking in men's tennis for the first time.

Top-ranked Caroline Wozniacki and 2010 French Open finalists Francesca Schiavone and Sam Stosur also reached the third round, while third-seeded Vera Zvonareva had to save a match point to advance.

On the men's side, No. 7 David Ferrer of Spain, No. 9 Gael Monfils of France, and former U.S. Open champion Juan Martin del Potro made it through.

Defending champion Schiavone cruised past Vesna Dolonts of Russia, 6-1, 6-2, winning 11 games in a row.

Djokovic, who won three clay-court tournaments leading up to Roland Garros and beat top-ranked Rafael Nadal in two of them, won seven straight games at one point and didn't face any trouble from his Romanian opponent.

Hanescu called for a trainer to look at his left leg after losing the second set. The trainer came back out after Hanescu held to make it 3-2 in the third.

Djokovic then won the next two points before Hanescu called it quits.

In the next round, Djokovic will face del Potro, who defeated Blaz Kavcic of Slovenia, 6-3, 6-2, 6-4.

"Well, it's a big challenge for both of us," Djokovic said. "He's a fantastic player who always deserved to be in the top five in the world, and I'm sure he's going to come back very quickly there, because he has amazing ground strokes and a big serve."

Federer defeated French wild card Maxime Teixeira, 6-3, 6-0, 6-2, to reach the third round.