Novak Djokovic lamented his dismal showing as Alejandro Tabilo profited from the world number one's "completely off" performance to triumph at the Italian Open.

Tabilo stunned Djokovic with a straight-sets victory in the third round on Sunday, winning 6-2, 6-3 in his maiden ATP Tour clash with the Serbian.

The Chilean advances to the fourth round at a Masters 1000 event for just the second time after Indian Wells in 2023, with Djokovic unable to explain his struggles in Rome.

"I just wasn't able to find any kind of good feelings on the court, to be honest, striking the ball. I was completely off," he said.

A six-time champion in Rome, the 36-year-old won his opening-round match at the ATP Masters 1000 event against Corentin Moutet.

However, Djokovic was inadvertently hit on the head by a falling water bottle when leaving the court after that victory.

Whether that incident impacted his performance against Tabilo remains to be seen.

"I don't know, to be honest. I have to check that," he said. "Training was different. I was going for [a] kind of easy training yesterday.

"I didn't feel anything, but I also didn't feel the same. Today under high stress, it was quite bad – not in terms of pain, but in terms of this balance.

"Just no coordination. Completely different player from what it was two nights ago. Could be. I don't know. I have to do medical checkups and see what's going on."

Tabilo's next opponent will be Karen Khachanov, who saw off Francisco Cerundolo 6-2, 6-4, while Djokovic is made to wait for his 1100th match win.