At last year’s French Open, Mackenzie McDonald tore his hamstring tendon three games into a first-round doubles match, requiring surgery that left what he called “a massive scar” and making it so the 2016 NCAA champion in singles and doubles for UCLA was unable to walk for about two months. On Wednesday, the 25-year-old American will be out on Court Philippe Chatrier, facing 12-time champion Rafael Nadal in the second round. “I know what it’s like on the worst end of it now,” he said Tuesday. “So tomorrow will be fun.” McDonald, who returned to the tour this year and is currently ranked 236th, called taking on Nadal at Roland Garros “probably one of the biggest challenges you can face in sports,” but he also said: “This year, I have the best chance that I would any year, with the balls, the speed, with how much lower it’s bouncing. I think I’m playing my best clay-court tennis I have played, and he hasn’t played too much this year. It’s a tough challenge, but I have to believe that I can beat him.” Another American faces another tough task at Court Suzanne Lenglen: Jack Sock meets No. 3 seed Dominic Thiem, who won the U.S. Open 2½ weeks ago and was the runner-up to Nadal in Paris in 2018 and 2019. Serena Williams takes on Tsvetana Pironkova in Chatrier in a rematch of the 23-time Grand Slam champion’s quarterfinal victory at Flushing Meadows, while No. 1 seed Simona Halep plays Irina-Camelia Begu in Lenglen.