Injured Nadal pulls out of Dubai

Nadal struggled in the final two sets against Murray in Rotterdam

World number one Rafael Nadal has joined Roger Federer in pulling out of next week's Dubai Championships.

Nadal struggled with a knee problem when he lost to Andy Murray in Rotterdam last weekend, and has decided to rest, on medical advice.

"The doctor has advised me to stay home and rest after the pain on my knee in Rotterdam," he said on his own website.

"Nothing to be worried about but it needs some rest. I ask my fans and the tournament organizers to understand."

Federer withdrew on Tuesday, and also pulled out of Switzerland's Davis Cup tie against the US from 6-8 March, to recover from a back injury.

Novak Djokovic and Britain's Murray will now be the top seeds in Dubai.

Federer has not played since he lost a five-set epic against Nadal in the Australian Open final.

"After injuring my back last autumn, I did not have enough time to strengthen it completely," said the 27-year-old.

606: DEBATE All the big players are getting injured at the moment ComonRafa

"I will use the next few weeks to make sure it is fully rehabilitated."

The 13-time Grand Slam champion had to withdraw from his third-round match at the Paris Masters in October, and had treatment on his back during his defeat by Murray at the Masters Cup in November.

Federer has often skipped the first round of the Davis Cup, returning only to help the team avoid relegation from the elite World Group.

However, the Swiss had committed to play alongside world number 18 Stanislas Wawrinka this year.

"This decision was very difficult for me," Federer said in a statement on his official website.

"I won't just be missing one of my favourite tournaments of the tour, but also the chance to go through to the next round with my team-mates."