Novak Djokovic says he is fully focused on trying to become world number one again at the ATP World Tours Finals in London.
Djokovic was replaced at the top of the rankings after he was knocked out at the quarter-final stage of the Paris Masters, as rival Andy Murray went on to win the tournament.
The Serbian has slipped to second position in the world and will need to show a considerable improvement in order to finish 2016 as number one.
Since winning the French Open to complete his Grand Slam collection, the 29-year-old has only managed to taste success once more which was at the Canadian Open in July.
The Belgrade-born star was runner-up at the US Open before exiting the 2016 Olympic Games in Rio at the first hurdle, losing to Argentina's Juan Martin del Potro.
Djokovic, who is the defending champion at the 02, would go back to world number one by defending his title and he insists it is a huge goal.
"It's one of the reasons why I'm here, to try to do as best as I can and eventually fight for the number one spot in the world," he said.
"Andy has an incredible last three or four months, actually, last six months, starting from the clay court finals, very consistent.
“The most consistent player this year without a doubt.
"He definitely deserves to be the number one player in the world. But we're coming to the final week of the year, we're all trying to get what's left in our bodies to the court and get as far as we can."