Dubai, UAE  - Rafael Nadal joined Roger Federer on the injury list for next week's Barclays Championships, with the Spanish No. 1 pulling out on Thursday to rest from a knee injury.

Nadal's website said that he had to cancel his trip to Dubai due to doctor's orders.

Separately, Federer withdrew with a back injury, which will also cause him to skip Switzerland's Davis Cup tie in Alabama against the United States March 6-8.

"I'm very disappointed not to be able to compete in Dubai but the doctor has advised me to stay home and rest after the pain on my knee in Rotterdam (final) last week," Nadal said on his website.

"(It is) nothing to be worried about, but it needs some rest. I ask my fans and the tournament organisers to understand and I am sorry for this.

"Dubai is one of my favourite tournaments and I have always played there."

Nadal said he hopes to be back on court in time for the Davis Cup against Serbia in Benidorm prior to Masters 1000 tournaments in Indian Wells and Miami in March.

The pullouts leave Novak Djokovic as top seed followed by Rotterdam champion Andy Murray. (dpa)