Novak Djokovic will be favourite to reach his 27th Grand Slam final when he faces Stefanos Tsitsipas in the French Open semis on Friday but what had been a smooth path through the draw has suddenly got a little rocky.
After his humiliating disqualification in the US Open fourth round when he inadvertently struck a ball in frustration into the throat of a line judge, Djokovic's French Open campaign has been remarkably uneventful.
But after winning his opening four matches without dropping a set he had to come from a set down to beat Pablo Carreno Busta in the quarter-finals, the player who directly benefited from his moment of madness in New York.
Djokovic, bidding for a second French Open and 18th Grand Slam title, still reached his 38th major semi-final relatively comfortably but for a set and a half against the obdurate Spaniard he struggled physically.
Afterwards he spoke of neck and shoulder problems and should he not be 100% fit against 22-year-old Tsitsipas, who is in only his second Grand Slam semi-final, it could be a long night on the Philippe Chatrier Court.
"I think Novak's injury is a big worry," former French Open champion Mats Wilander, a Eurosport analyst, said. "It's a legitimate injury and if he doesn't get a good start then that could be a problem."
Tsitsipas, the fifth seed, was thrashed by Rafa Nadal in his previous Grand Slam semi-final last year in Melbourne, but ended 2019 by winning the prestigious ATP finals.
After a stuttering start in Paris when he trailed Spain's Jaume Munar by two sets, Tsitsipas has been blemish-free, winning 15 consecutive sets although one was not completed after Aljaz Bedene retired injured in the third round.
Tsitsipas will need his renowned shot-making skills to break through the Djokovic wall, however, whether the Serb is fully fit or not. He has done it twice before in Masters 1000 events but has never met Djokovic on a Grand Slam stage.
Remarkably, Djokovic's only "defeat" in 36 matches this year was his default, but he will be wary of a player hungry to make his Grand Slam breakthrough.
"He's been playing the tennis of his life really in the last 12 months," Djokovic said. "Winning World Tour Finals, just being very consistent on all surfaces with his results.
"I expect a really tough, tough match."