Novak Djokokovic's coach Andre Agassi has backed the Serbian to come back into contention for titles after watching Rafael Nadal and Roger Federer turn back the years to sweep the tennis circuit, winning all four slams this year, two a piece.

Djokovic started the year as the number two ranked player in the world. However, he has currently fallen to number seven after what has been a poor, injury-ridden year.

The Serbian performed poorly in the Grand Slams — his best showing came in the form of quarter-final exits at the French Open and Wimbledon. Djokovic last featured competitively in his Wimbledon quarter-final clash with Tomas Berdych, with the Serbian ace retiring midway through the match due to an elbow injury.

Having taken time off until 2018 to recuperate, the 30-year-old is likely to drop out of the top 10 by the time he returns to action. The 12 Grand slam winner has been going through a poor run, but Agassi insists that there is no reason why he cannot make a comeback and emulate the feat of the legends who swept the courts this year.

"How can you ignore the beauty of what we've seen with Federer and Nadal this year? To write anybody off is a mistake," Agassi said, as quoted by Sky Sports.

"Novak is really one of those talents that if he feels right on the tennis court it doesn't matter who's on the other side of the net. I was one of those players where it was about being better than one person and keeping it as simple as that and figuring a way to get past that.

"If you can take a talent of [Djokovic's] magnitude, somebody who can shut down a court the way he can, play offense the way he can, and get him to realise there's another human being on the other side of the net and all you have to do is be better than that guy. I think you are really going to see something special from him."