Roger Federer has issued a warning to Novak Djokovic against taking an extended break as the Serbian continues to suffer through an elbow injury. 

The 18-time Grand Slam winner took six months off following his defeat to Milos Raonic last year and is the heavy favorite to clinch the title this time around after knocking out the same opponent. 

Djokovic hinted at taking time off from the sport in order to repair his elbow after retiring from his match against Tomas Berdych, but Federer had words of caution for the 30-year-old as well as other competitors. 

"It’s normal. Once you hit 30, you’ve got to look back and think of how much tennis have I played, how much rest did I give my body over the years, how much training have I done, did I do enough, did I overdo it or not enough," he said after beating Raonic.

"It’s always calibrating the whole thing. For me it worked out. Doesn’t mean it’s going to work out for everybody.

"But sometimes maybe the body and the mind do need a rest. Who knows. You just want to take that decision early enough or see it coming and anticipate.

"The problem is you can only play with a certain injury for a certain amount of time, because what you don’t want happening is that it becomes chronic.

"Then even a surgery can’t help you that much any more. That’s why I’m happy I’ve had to take my first surgery really only at 34, 35 years old. That was a blessing. I’m happy about that."

The Swiss legend was quick to wish both Djokovic and Murray well, with the latter suffering a hip problem during his unexpected defeat to Sam Querrey. 

Despite not being surprised that the Serb encountered injury concerns at this stage of his career, Federer still hopes that Djokovic returns stronger and better. 

The 35-year-old added: "I mean, you wish them well right away as a rival to them and a friend. You want them to be healthy again. It does happen, you know. Novak’s not missed any slams basically.

"I don’t want to say sooner or later these things unfortunately happen, but he’s played a lot of tennis in recent years.

"For him to be hurt at some stage is only but normal. That’s why we want him to recover quickly."