Novak Djokovic's coach Andre Agassi has confirmed that the Serbian has been suffering from an elbow fracture but will know in a matter of days if the injury is behind him, allowing him to return to the court.

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

Agassi is confident that Djokovic can return to his best and compete with the likes of Roger Federer and Rafael Nadal, who swept the Grand Slams in 2017. 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.

"He's done fantastic work in making sure he's over his injury once and for all, which was a fracture in the elbow," Agassi told ESPN. "We'll know in a week from now if that's fully behind him, which is great. He's used the time [off tour] to train -- a lot."

Agassi was also asked to comment on the likelihood of a surprise at the ATP World Tour finals in which apart from the usual stars, there are a host of debutantes who can challenge for the title. Nadal, Dominic Thiem, Grigor Dimitrov and David Goffin are in Group Pete Sampras, while Federer, Alexander Zverev, Marin Cilic and Jack Sock constitute Group Boris Becker. Dimitrov, Goffin, Zverev and Sock are making their debut in the year-end event.

"I haven't studied it much, to be honest. My focus has been the big picture moving forward with Novak. Obviously, watching what Alexander Zverev has done this year, he's been pretty spectacular. There are a few guys in there for a first time, so it's hard to predict. Some are going to be nervous and some are going to overachieve. It's a great format for fans. It's a great arena. I'll enjoy watching it -- but I'm out of the prediction business!" Agassi added with a smile.

Novak Djokovic
Andre Agassi is confident Novak Djokovic can return to winning ways in 2018 Getty