Los Angeles: Roger Federer's former coach Paul Annacone has asserted that the tennis star can return from six months out with injury and win another Grand Slam.

"Last year was a very tough year for him and he still got to the semis of Wimbledon," Annacone, who coached the Swiss ace from 2010 to 2013, told BBC Sport on Sunday.

"There is no reason why he can't play at that level again."

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Federer, a winner of 17 majors, is due to make his comeback from a knee injury against Britain's Dan Evans in the Hopman Cup in Perth on Monday.

"When you look at his track record, particularly on grass, if he's healthy, it's going to be very difficult not to put him in the sentence as one of the favourites.

"Again, it's about staying healthy, but I absolutely think he can contend for a major title," Annacone said.

Federer is yet to set foot on court since hurting his left knee after losing in the Wimbledon semi-finals to Milos Raonic in July.

But Annacone believes Federer's extended absence "could be a positive".

"It's given him time to refresh and really get his body healthy.

"Six months isn't critical -- it's not what I would call lethal. I know how hard Roger's worked and how professional and meticulous he is about his preparations," the American said.

"It is a challenge, but great players love challenges. I expect great things because he's a great player."

Federer had a knee surgery in February 2016. He last won a tournament in November 2015 -- the Swiss Indoors -- and has not won a Grand Slam since Wimbledon 2012.