Djokovic tells critics to give Federer a break

World number one Novak Djokovic leaped to the defence of Roger Federer, telling critics of the slumping Swiss to give the 17-time major winner a break.

Federer suffered a stunning US Open fourth-round straight-sets upset at the hands of Spanish 19th seed Tommy Robredo on Monday.

It is the first year since 2002 that the 32-year-old has not made a grand slam final and sparked feverish speculation over his future in the sport with the loss to Robredo coming on the heels of a second-round exit at Wimbledon.

"Roger did not play close to his maximum level so it's always a question of why is he not playing well. People need to give him a break a little bit, because I think it's normal to expect that he's not moving as well as he did when he was number one and he was so dominant," said the Serb.

"For me, he's still playing really well and definitely deserves to be one of the top five players in the world, no question about it."

Djokovic said he would not be advising Federer on what his future plans should be despite his rival having slipped to seven in the world, his lowest ranking for over a decade.