Djokovic begins preparations with hopes of challenging top-ranked duo Nadal and Federer in 2018

Novak Djokovic has begun preparations for the 2018 season after confirming that Andre Agassi had arrived in Monte Carlo to join him and newly appointed coach Radek Stepanek.

The Serbian has not played since his loss in the quarter-finals at Wimbledon earlier this year and will return to action for the first time at the Qatar Open in Doha during the first week in January. He ended his 2017 campaign prematurely due to an elbow injury.

Djokovic has struggled for form since winning the French Open in 2016 and lost his number one ranking to Andy Murray the same year. He managed just two titles this year and parted ways with his entire coaching team, including long-time coach Marian Vajda, ahead of the French Open in 2017.

The 30-year-old, who has been the dominant force in the game in recent years, appointed Andre Agassi as his head coach and will be hoping to turn his fortunes around and get back to winning ways in 2018. The American is no stranger to Djokovic's situation as he too underwent a similar drop in form during his career.

Agassi is unlikely to travel with Djokovic throughout the year and his main focus will be the four Grand Slams and a few other major tournaments. Stepanek, who recently retired from the game, will be the Serbian's full-time coach during the 2018 campaign.

The American former world number one, however, has travelled to Monte Carlo to help Djokovic in his preparations for the new campaign after which he is likely to return to the United States. Agassi will later rejoin with Djokovic in Australia ahead of the first major of the year.

"Lots to be done, but we embrace it with lots of excitement. Practice today with Andre Agassi and Radek Stepanek," Djokovic posted on his official Twitter account alongside a picture of the trio in a practice court in Monte Carlo.

In Djokovic's absence, Rafael Nadal and Roger Federer have returned to the fore after a dominant 2017 campaign where the duo won a combined 13 titles, which includes sharing the four Grand Slams between them with two apiece.

Nadal and Federer will start the year as the ATP's top-two ranked players, while the Serb will begin the campaign ranked number 12 in the world.