Kei Nishikori, whose ascent to No. 9 in the latest world tennis rankings made him the first Japanese man to break into the top ten, spoke on Tuesday about his anticipated return from injury for the year's second Grand Slam event and his commitment to becoming one of the world's top five players.

"I believe I'll be able to play in the French Open," Nishikori said in a media conference call from his Florida practice facility, where he is currently recovering from the back injury that forced him to retire from the Madrid Open final against world No. 1 Rafael Nadal on Sunday. "I was in pain since the (Madrid quarterfinal) match against Feliciano Lopez. Now, there is still a bit of stiffness when I walk.

"Considering how well I've played on clay courts recently, I expect myself to keep it going (at Roland Garros)."

After starting the year ranked No. 17 in the world, Nishikori defended his title in Memphis in February and won ten straight clay-court matches from late April into May — which included becoming the first Japanese ever to capture the Barcelona Open — en route to his current No. 9 ranking.

The Japanese ace credited his new coach and former French Open champion Michael Chang for boosting his game, but also made it clear he aims for further improvement.

"(Chang) has me coming in from the baseline more often and playing a more aggressive brand of tennis than last year," Nishikori said.

"If I can stay in the top 10 for about a year, I'll have a sense of what it feels like to be at this level. My next goal would be to make it into the world's top five."