Novak Djokovic revealed he is not happy with his form heading into the US Open next week.
The final grand slam of the year kicks off on Monday in Flushing Meadows in New York and the Serb, who won the Australian Open and Wimbledon earlier in the year, is concerned about his game.
The world number was dominated by a flawless Rodger Federer in the final of the Cincinnati Masters on Sunday, losing in straight sets. Reflecting on his tournament, Djokovic indicated his form was patchy at best.
"Played a couple good matches and couple not-so-good matches," the 28-year-old told tennis.com.
"Still not very happy with my form and with my game, but I have a week to work on it. Conditions in New York suit me a little bit better, so I look forward to it."
Cincinnati has not been a happy hunting ground for Djokovic, though he still feels the evetn plays a crucial role in his preparation for the hard courts of the Billie Jean King Tennis Centre.
"Of course it was playing an important role in my approach to this tournament," he added.
"It does every year for last couple years. This year I got to the finals, step closer. Let's see. I'm going to keep going, keep fighting to make the history.
"Obviously it's a great incentive and inspired me to come back and play my best tennis."
The nine-time grand slam winner will be looking to make amends for his semi-final loss to an inspired Kei Nishikori in 2014.