Tennis superstar Novak Djokovic has revealed that he is highly motivated and has a lot of gas left in the tank as he looks to reclaim his number one ranking from the Scot Andy Murray. The Serb who lost his top ranking to Murray earlier this month, will be entering the ATP World Tour Finals in London as the second-ranked player for the first time since 2014.

The 29-year-old recently admitted that the loss of desire and love for the sport was behind his poor form and that private and injury issues had affected his performance on the court. However, the Serb has made it clear that he is still committed to his career.

"I have plenty of motivation and it starts from within. Even after 10-plus years at a professional level, I still feel I have a lot of gas in the tank. I feel like I have a lot more years ahead of me. I feel great joy when I compete, when I play", Djokovic said, as quoted by

"The power of passion towards the sport is the No.1 thing that drives me to play, to enjoy to play. This is the game. If you don't enjoy the game, your time on the court, everything else becomes two or three, five times more difficult than it is or should be," he added.

The Serb who has won just one title since the French Open this year can retain his number one ranking if he goes through the upcoming ATP World Tour Finals unbeaten. Ahead of the event, the former world number one had nothing but praise for the man who toppled him from the top spot.

"He's definitely a well deserved No.1 at this point. Whether or not he can sustain it is a good question for me. The qualities he possesses as a player, his determination to the sport, there's a good chance that he can still play in this level for some time."

The 2016 ATP World Tour Finals event takes place from 13-20 November with the top eight players battling it out for the end of season bragging rights at the O2 Arena in London.