Roger Federer is turning his attention to Rome following his withdrawal from the Madrid Open with a back injury.

"The goal clearly now is to play there and do well," said the third-ranked Federer, who has been mostly injury-free during his career but has recently run into some physical problems.

He was ill before the tournament in Brisbane and required surgery to repair a torn meniscus following the Australian Open. The 17-time Grand Slam champion withdrew from the Miami Open because of a stomach virus and injured his back during practice before Madrid. Aside from Brisbane and the Australian Open, the only other tournament he has played is Monte Carlo, where he reached the quarterfinals.

"I mean, I am frustrated," Federer told the press in Madrid. "At the same time, I'm still upbeat … I would rather have it being the back rather than the knee ... This is normal back things I've had in the past, which I guess is good because I know how to handle it. I know how long it can take. Sometimes it can vary by a few days here and there."

Federer, who originally had just Monte Carlo on his warm-up clay-court schedule but planned to add more tournaments as desired, is looking to his training to make up for a lack of match play.

"I've been playing a lot of practice on clay,” he said. “I've been putting a lot of hours in. I was [there for] 10 days in Monaco before the tournament and played three matches there … Now, also the last two weeks, I was back on the clay even though it was cold in Switzerland. Maybe that didn't help my back. I'm not sure, but I practiced there for many days as well.''

He insisted that the schedule changes will not hamper him at the French Open.

“With my experience and the way I feel about big tournaments, if I have matches, great,” he said. “If I don't, I trust my game that I'll be fine, regardless."

Federer could still move up to No. 2 in the rankings following Madrid, depending on the performance of defending champion Andy Murray.