Russian Daniil Medvedev was disqualified from his China Open semi-final clash with Novak Djokovic after hitting a rebounding ball into the crowd, striking a spectator in the eye.
World number five Medvedev was trailing 7-5 5-3 on Monday and had lost a point when he hit the ball coming off the wall.
The spectator, who was sitting in the first row, clutched his left eye and appeared to be in pain as he walked out of the gallery, assisted by stadium staff.
"I was shocked, to be honest... I hope that person is not badly injured," said sixth seed Djokovic, who was disqualified from the US Open in 2020 under similar circumstances.
"On the other hand, I also feel sorry for Daniil because I know exactly how it feels to be disqualified in a big match ... I'm sure that Daniil didn't want to do this intentionally."
Both semi-finals ended prematurely in Beijing as Hubert Hurkacz retired with an adductor injury earlier on Monday.
Australian Alex de Minaur was leading the first semi 6-4 3-2 when his Polish opponent, who had struggled with movement throughout the match, retired.
Defending champion Carlos Alcaraz overcame early wobbles on his serve to outclass fellow Spaniard Jaume Munar 5-7 6-3 6-1 and reach the Japan Open final on Monday, taking a step towards his first singles title after his comeback from a wrist injury.
The UAE Football Association (UAEFA) has provided 12 chartered aircraft to transport fans to Jeddah to witness the UAE national team's final match against Saudi Arabia in the Gulf Cup on Tuesday.
Title holders Portugal have maintained their 100 per cent record in the Nations League with a 2-1 home win over Norway on Sunday to seal a place in the March quarter-finals and shift the focus further away from Cristiano Ronaldo's abrupt exit from the squad last week.
Formula One's governing body has promised a full investigation into a software bug that caused chaos and forced the start of Sunday's Bahrain Grand Prix in Malaysia to be aborted with drivers feeling like they were in battery-powered cars made of Lego.
His Highness Sheikh Mansour bin Mohammed bin Rashid Al Maktoum, President of the United Arab Emirates National Olympic Committee, praised the success of the UAE athletes for their historic medal haul in the 2026 Asian Games in Japan.