Federer out of Madrid Open with back injury

Former world number one Roger Federer has pulled out of this week's Madrid Open with a back injury.

The Swiss great travelled to the Spanish capital for the tournament but was unable to practice and announced his withdrawal on Monday.

"I don't want to take any more chances. I'd rather play it safe," the 17-times grand slam champion told a news conference.

Federer, however, said he would be back for the Rome Masters next week.

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