Alexander Zverev has been slammed for appearing to spit towards a fan at the Monte Carlo Masters.
The young German cut a frustrated figure as he advanced to the quarter-finals with a tough win over Jan-Lennard Struff on Thursday.
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Zverev initially received a telling off from chair umpire Mohamed Lahyani after throwing an advertising sign that was sitting on the court.
Earlier in the week Aussie Thanasi Kokkinakis slipped on a similar piece of advertising and injured his knee, putting him in doubt for the French Open.
"Kokkinakis broke his knee cap when he fell on one of those," Zverev told the umpire, clearly unimpressed that he'd received a dressing down.
And Zverev's mood only got worse as he angrily smashed his racquet in the second set, before appearing to spit in the direction of a spectator.
Sky Sports pundit Annabel Croft slammed Zverev's 'disgusting' actions.
"Spitting the way that he did is pretty disgusting," she said after the match.
"It shouldn't be allowed and I'm sure there will be some sort of repercussions."
Zverev was made to work hard before closing out Struff, 6-4 4-6 6-4.
He was broken to love serving for the match at 5-2 and wasted his first match point when Struff served at 30-40 in the next game.
Struff could have made it even harder for Zverev, but he missed an easy volley at the net at 30-30.
Instead of giving him break point, it gave Zverev a second match point. He took it when Struff hit a powerful forehand narrowly wide, and let out a yell of relief.
Meanwhile, World No.1 Rafael Nadal cruised to a 6-3, 6-2 victory over Russian Karen Khachanov to set up a "difficult" quarter-final against Dominic Thiem, after the Austrian stunned Novak Djokovic.
Nadal needs to win an 11th Monte Carlo title to stay clear of Roger Federer at the top of the world rankings, and the 16-time Grand Slam champion made short work of Khachanov.
Khachanov held his own at times in the opening set, but Nadal moved through the gears and claimed his second comfortable victory of the week after his opening win over Aljaz Bedene.
"A good victory. Straight sets against a difficult opponent. That's the real thing," said Nadal.
Thiem should provide a sterner test in the last eight, after the fifth seed came from a set down to beat Djokovic.