Novak Djokovic has been beaten at the Italian Open before the quarterfinals for the first time, saying he has been off kilter since a water bottle fell on his head. 

Djokovic lost his third-round clash with 29th-seeded Chilean Alejandro Tabilo in straight sets — 6-2, 6-3 in 67 minutes — marking the first time in 18 trips to Rome that he has not made it to the last eight. 

The match ended with Djokovic bombing a second serve down the middle but missing the mark and serving his fifth double fault for the match. 

Djokovic also missed almost half of his first serves, landing 27 out of 52, and hit just 14 winners with 12 unforced errors, compared to Tabilo's 22 and four. 

A six-time champion and six-time runner-up in Rome, Djokovic said he had struggled with balance and coordination since a water bottle fell on his head while signing autographs after beating Corentin Moutet in his opening match. 

He made light of the incident by making his way to practice courts in between matches wearing a bike helmet. 

But when the 36-year-old was asked whether he was affected by the incident in his loss to 26-year-old Tabilo, he suggested he was.

"I don't know, to be honest. I have to check that," Djokovic said. 

"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 check-ups and see what's going on."