World number one Novak Djokovic collapsed to the ground after he was struck on the head by a bottle at the Italian Open on Friday.
Djokovic, still to win a title this year, recovered from a slow start to see off lucky loser Corentin Moutet and move into the third round in Rome.
But just moments after his victory, the 36-year-old suffered an "accidental" blow to his head as he made his way off the court.
Djokovic fell to the ground for more than half a minute before he returned to his feet, flanked by multiple officials, and then headed to the medical centre.
A statement from the Italian Open read: "Novak Djokovic has been accidentally hit by a bottle while signing autographs after his 6-3 6-1 win against France's Corentin Moutet at the Italian Open.
"This is not being treated as a deliberate act, but as an accident. A boy was calling out to get an autograph and the bottle fell out of his bag. Novak has been taken to the medical centre."
Djokovic had made a nervy opening to the first set as Moutet broke twice to move 3-1 ahead.
The Serbian, though, fought back with two breaks of his own before serving out the opening set in 45 minutes.
There was a light-hearted moment at the start of the second set when the alarm on Moutet's phone in his bag went off, with the Frenchman making a quick dash to his chair to hit the stop button.
With Djokovic 2-0 up after an early break, the world number one noticed a hole near the baseline on his side of the court, which was quickly patched up before extra clay was bedded in during the next change of ends.
After such a promising start, Moutet was beginning to lose his cool – and was warned by the umpire after kicking the net in frustration after sliding in for a forehand.
Djokovic – competing in his first match since the semi-finals in Monte Carlo – kept the pressure on Moutet's serve to bring up a match point, which he took at the first opportunity with a forehand volley to complete his 6-3 6-1 win.
Former champion Alexander Zverev, the world number three, defeated Aleksandar Vukic 6-0 6-4 while veteran Bulgarian Grigor Dimitrov swept past Yoshihito Nishioka 7-5 6-4 on Court 12.
Fifth seed Casper Ruud, though, suffered a shock defeat as Miomir Kecmanovic came from behind to win 0-6 6-4 6-4 – the Serbian having recovered after leaving the court for a medical time-out late on in the first set.
Number 11 seed Taylor Fritz ended the hopes of home wildcard Fabio Fognini as the American came through 6-3 6-4.
Ben Shelton maintained his impressive clay-court form as the 21-year-old American came from behind to beat Pavel Kotov 4-6 6-3 6-4 and reach the third round in Rome for the first time.
Portugal's Nuno Borges knocked out 15th seed Alexander Bublik 6-4 6-4 and Brazilian qualifier Thiago Monteiro was a 6-1 6-3 winner over Australian number 32 seed Jordan Thompson.
Luciano Darderi and qualifier Francesco Passaro delighted the home support with wins over seeds Mariano Navone and Tallon Griekspoor respectively.
