Djokovic's barren run ahead of Roland Garros continued as the 24-time Grand Slam winner was beaten 6-4, 0-6, 6-1 by Tomas Machac in the Geneva Open semi-finals on Friday, weeks after losing heavily to Alejandro Tabilo in Rome.

The 37-year-old Serb is struggling to regain his rhythm with many fearing that his erratic form could spell trouble for his bid for a fourth Paris crown.

"Of course I am worried... I haven't been playing good at all this year," Djokovic told reporters after being beaten by Machac on Friday.

Asked about his title defence at Roland Garros, Djokovic said: "(I’ve had) some (good) matches here and there but it is what it is. You have to accept it. I don't consider myself a favourite there.

"I have a lot to work on. I’m going to take it match by match and see how far I can go."

During the final moments of the first set, Djokovic requested a medical pause due to a stomach issue. Earlier in May, he was hit on the head by a fan's water bottle while signing autographs.

"I just need to feel better. It’s not enjoyment when you are suffering on the court feeling this way," he added.

"You're not able to focus on tennis when you have other stuff happening. I just hope I can be fit and ready and prepared for Roland Garros."