Roger Federer believes Andy Murray's poor performances this year can be easily explained.

As anticipation for Wimbledon grows ahead of the tournament, Federer has spoken out on his rivals for the crown, naturally focusing on the World Number 1 and reigning champion Murray.

Federer was talking on his return to the tour, having taken an 11-week break to ready himself for the grass court slam. And with there being no standout performer so far this year, many consider the 35-year-old to be something of a favourite for the title.

The Swiss legend says one player's form can be explained, though.

"I think Andy was just extremely tired after getting to World No.1 at the end of last year. so there was maybe a bit of letdown and then he was injured too, so that didn't help," Federer said, as per Eurosport.

Murray has undergone a very poor 2017 since becoming World No.1 at the end of 2016. The year started with a defeat in the Qatar Open final to Novak Djokovic, before a fourth round exit in the first Grand Slam of the year at the Australian Open.

Despite following up that disappointment with victory at the Dubai Tennis Championship, Murray has suffered early round exits in four tournaments, including most recently in a first-round straight-sets defeat at Queen's Club to unseeded Jordan Thompson.

But Federer clearly believes Murray will bounce back soon, going on to say "I think the second part of the season will be really crucial for Andy, and Novak [Djokovic] as well. I think the second half of the season is going to be really, really interesting.”

One player who is going into Wimbledon on a high, however, is French Open winner Rafa Nadal. Nadal made history in winning the tournament for the tenth time in his career, a feat no man has ever accomplished.

And Nadal's success prompted great praise from his long-time rival: "I think what Nadal did at the French Open stands out," Federer added.

"The best players were in the final and Rafa once again cemented himself as maybe the greatest clay-court player of all time."