Coco Gauff looked to be cruising against Donna Vekić in her third-round singles match at the Paris Olympics. Then, all of a sudden, she wasn’t.

Having been a point away from taking the first set at Roland Garros, Gauff had to watch the contest slip away from her, eventually succumbing to a 7-6(7) 6-2 upset defeat on Court Philippe-Chatrier.

The most fraught moment of the match came midway through the second set when Gauff was reduced to tears during a heated exchange with chair umpire Jaume Campistol.

A line call on Gauff’s baseline was initially deemed out, but Campistol overruled the decision and handed Vekić a crucial break point. Play was then paused as the American vehemently argued that the point should be replayed as the call was made just before she hit the ball.

The supervisor also came onto the court and the ensuing debate lasted five minutes, with Gauff wiping tears away from her eyes. Boos and jeers came from the crowd when play was eventually resumed.

“There’s been multiple times this year where that happened to me, where I feel like I always have to be an advocate for myself on the court,” she later told reporters.

“And I feel like in tennis, we should have a VR [video review] system because these points are big deals. Usually, afterwards, they apologize, so it’s kind of frustrating when the sorry doesn’t help you once the match is over.”

Gauff immediately created three break points the following game, but Vekić shut down the opening, saving the last point with an inch-perfect lob before taking a 4-2 lead in the second set.

The match was firmly in the Croatian’s control from that point, and she closed out the contest to set up a quarterfinal meeting with either Greece’s Maria Sakkari or Ukraine’s Marta Kostyuk.

“Donna played well,” said Gauff. “She’s been playing well throughout Wimbledon ‘til now, so I knew it would be a tough match. I think I had a lot of chances in the first, and I felt like if I could clinch that set, it might have helped me in the momentum of the second.”

The match was played in the baking midday sun with temperatures expected to reach 95 degrees Fahrenheit (35 degrees Celsius) in Paris, though adding in the humidity, the heat index was 104 degrees F (40 degrees C) – easily the hottest day of the Olympics so far.

On Court Philippe-Chatrier, sun hats and hand-held fans were out in force, and an automated stadium announcement between games reminded spectators to drink water and take regular breaks from the heat.

Gauff collapse

Gauff, the world No. 2 and a strong pre-tournament contender to medal in the women’s singles event, stormed into an early first-set lead, but after seeing a set point saved by Vekić, she lost her break advantage when a forehand drifted wide.

As the set wore on, Vekić played the shot of the match at that point, pushing a smash back past her opponent. But Gauff responded in similar fashion the following game, returning a Vekić smash with a well-timed backhand while her opponent was stranded at the net.

Both players had set points in the tie-break, but it was Vekić who capitalized on the opportunity, raising her level when it mattered to take a one-set lead in more than an hour.

Vekić, a semifinalist at Wimbledon earlier this month, lost an early break with a double fault at the start of the second set, but she managed to take the next five games in a row and wrap up the victory in brutal conditions.

“It was very, very tough out there, the conditions, when we warmed up this morning and the roof was closed,” Vekić told reporters. “It took me a couple of games to adjust; it was very hot. The ball was flying a little bit, but after that, I got in rhythm and it was pretty good.”

The dispute with the umpire in the second set, Gauff later explained, didn’t alter the result of the match.

“I’m not going to sit here and say one point affected the result today because I was already on the losing side of things before that point happened,” she said.

The 20-year-old, a flag bearer for Team USA at the opening ceremony, still has mixed and women’s doubles competitions to come in Paris having won her opening match in the latter alongside Jessica Pegula on Saturday.