The world number one said how he felt on court on Sunday was "completely like a different player entered into my shoes. Just no rhythm, no tempo, no balance whatsoever on any shot".

"It's a bit concerning," he added.

Djokovic, a 24-time grand slam champion, was beaten in round three in Rome by 26-year-old Chilean Alejandro Tabilo, who won the match 6-2 6-3 in just 67 minutes. It was one of the Serbian's worst displays at one of his favourite tournaments.

The 36-year-old sports star was signing autographs on Friday following an earlier win when he collapsed on to the ground after the container, which fell out of a spectator's rucksack, struck him from above.

Speaking on Sunday about the incident, Djokovic said: "It was unexpected obviously. I wasn't even looking up. Then I felt a very strong hit in the head. That has, yeah, really impacted me a lot. Been through half an hour, an hour of nausea, dizziness, blood, a lot of different things.

"I managed to sleep okay. I had headaches. The next day was pretty fine, so I thought it's okay. Maybe it is okay. Maybe it's not."

The top seed added: "I didn't do any scans or any tests. Right now, I feel like I should do it, so I will do it and let's see. Let's see what's happening."

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Djokovic wears cycling helmet to sign autographs

Djokovic had lost only once before to an opponent outside the top 10 in the Italian Open, where he had never gone out before the quarter-finals.

The six-time champion had just 14 winners, committed 12 unforced errors, served five double faults and failed to create a single break point in Sunday's match.

Tabilo, the 29th seed, said: "I was just trying to keep my nerves in, keep swinging. Obviously every time you feel you're closer to the end your arm starts to get a little tighter so I was just trying to not think about it, take it point by point and it's crazy.

"I can't believe what just happened."

Following the bottle incident, Djokovic stayed on the ground for a while before being helped by a security guard to the changing rooms.

He was checked over by doctors, according to tournament organisers, and did not attend his usual post-match news conference.

However, Djokovic said in a post on X on Friday that he was "fine" and resting at the hotel "with an ice pack".

"Thank you for the messages of concern," he wrote.

"This was an accident and I am fine resting at the hotel with an ice pack. See you all on Sunday."

On Saturday, Djokovic wore a cycling helmet as he signed autographs for fans while training at the tournament.