PARIS -- Australian Adam Walton, the 97th-ranked player who received a wild-card invitation into the French Open, beat former world No. 1 Daniil Medvedev in a five-set, first-round match in unusually hot conditions at Roland Garros on Tuesday.
Walton prevailed 6-2, 1-6, 6-1, 1-6, 6-4 in a match that took 3½ hours to complete.
For a third consecutive day, the temperature in Paris was forecast to rise to at least 32 degrees Celsius (90 Fahrenheit), making net-rushing -- which is usually better reserved for hard and grass courts -- a viable option because the court is drying out quicker and playing faster.
Medvedev, the No. 6 seed, made four consecutive errors in the deciding game while on serve, including a double fault, to give Wilson his first career victory against a top-10 player.
It was Medvedev's second straight first-round exit here and third in four years.
"I know why I don't really play my best in Roland Garros, but if I say it, it's (making) excuses," Medvedev said. "So I keep it to myself."
In other matches, Stefanos Tsitsipas, the 2021 runner-up to Novak Djokovic, was leading 6-2, 3-0 against Alexandre Muller when his French opponent retired with a right calf injury.
Muller wiped away tears as he left the court, with the injury coming three months after he hurt his left calf.
Alexander Blockx, meanwhile, withdrew from the tournament with a right ankle sprain, making Alex de Minaur -- his scheduled second-round opponent -- the first player into the third round.
Britain's Cameron Norrie, the No. 20 seed, retired midmatch for just the second time in his professional career in the opening round at Roland Garros. The 30-year-old, playing with a rib injury, trailed Adolfo Daniel Vallejo 7-6 (7) 2-0 when he halted the match after 79 minutes.
Jan-Lennard Struff of Germany ousted Alexander Bublik, the No. 9 seed, 7-5, 6-7 (6), 6-4, 7-5.
French teenager Moïse Kouamé made the perfect start to his French Open career with a 7-6 (4), 6-2, 6-1 win against veteran Marin Cilic.
The 17-year-old Kouamé raised his arms in triumph and tilted his head back after defeating the 37-year-old Cilic, who won the 2014 US Open, finished runner-up at two other majors, and reached the French Open semifinals in 2022.
The ATP Tour said No. 318-ranked Kouamé became the first man born in 2008 or later to win a Grand Slam match, and the crowd on a sun-baked Court Simonne-Mathieu showed their appreciation by chanting "Mo-ïse! Mo-ïse! Mo-ïse!" and clapping in between.
"It's not easy to stay in the present without thinking of the score," Kouamé said. "It wouldn't have been possible without the huge help you (the crowd) gave me."
In March, he became the youngest winner in Miami Masters history when he beat Zachary Svajda in the first round -- earning a congratulatory message from Djokovic.
Other seeded players to advance Tuesday included Valentin Vacherot (16) and Learner Tien (18). Tallon Griekspoor (29) and Corentin Moutet (30) were among the seeded players to fall.
The Associated Press contributed to this report.