Frances Tiafoe advanced to the third round of the US Open on Wednesday when Alexander Shevchenko retired in the third set with the 20th-seeded American leading 6-4, 6-1, 1-0.

Tiafoe, who reached the US Open semifinals in 2022, was in complete control when Shevchenko, who had the trainer out after the second set, suddenly called it a day.

“Happy to get it done. Hate to win it that way but overall I thought I actually played pretty well today,” Tiafoe said after a stress-free victory during which he changed shirts five times.

Tiafoe broke Shevchenko to take the first set and grabbed a 5-1 double-break lead in the second before serving out the one-sided match.

Tiafoe has now won 11 of his past 15 matches since bringing David Witt on as his coach in Atlanta, highlighted by a run to his first Masters 1000 final in Cincinnati. Prior to that, Tiafoe had a 15-15 record at the tour level this season through Wimbledon.

Witt has been Venus Williams’ longtime coach for 11 years, and has also worked with Jessica Pegula and Maria Sakkari.

Up next for Tiafoe could be compatriot Ben Shelton if he defeats Spain’s Roberto Bautista Agut when the two close out the day session on Grandstand.

In other men’s singles results from Wednesday, Alexander Zverev dispatched Alexandre Muller 6-4, 7-6 (5), 6-1 on a sweltering Louis Armstrong Stadium court.

Zverev is now one win shy of 100 career major match wins and is inching closer toward joining Boris Becker (163) and Tommy Haas (105) as the only German men to win 100+ major matches.

The big-serving fourth seed blasted 15 aces and employed a drop-shot finesse at the net to preserve his hopes of capturing a career-first major after a runner-up finish at Roland Garros.

Zverev proved too much for world No. 77 Muller, who committed 41 unforced errors and battled through an apparent leg injury in brutal temperatures and high humidity at Flushing Meadows.

The German came out firing after a shaky first-round performance, breaking Muller’s serve in the first game before ultimately claiming the back-and-forth first set.

Clutching his upper right leg, Muller left the court for a lengthy medical timeout between sets but returned with a vengeance. He was two points from taking the second set, but Zverev fought back to take the final five points of a tiebreak, blasting a line-hugging forehand for the winner.

Zverev cruised through the third set, closing out the match with a final ace to set up a third-round meeting with Tomas Martin Etcheverry, who beat fellow Argentinian Francisco Cerundolo 6-3, 4-6, 6-4, 1-6, 6-3.

Zverev said he was pleased to get through in three sets given the “very hot, very humid” conditions.

“I was at some point very, very wet. The whole court was flooded from me,” Zverev said. “But I felt good physically.”

Another men’s third-round matchup will have No. 9 seed Grigor Dimitrov, who reached the US Open semifinals in 2019, against Tallon Griekspoor. Dimitrov swept past Rinky Hijikata, while Griekspoor advanced when No. 21 seed Sebastian Baez stopped playing in the second set of their match.

Taylor Fritz, the highest-ranked American in the men’s draw at No. 12, caps play in Louis Armstrong Stadium against Italy’s Matteo Berrettini, with defending champion Novak Djokovic on the schedule Wednesday night in Arthur Ashe Stadium.

With temperatures reaching into the 90s, the extreme weather policy was in effect Wednesday at the Billie Jean King National Tennis Center, meaning players were allowed a 10-minute break between the third and fourth sets if either player requested a break. If both players decline a 10-minute break, play shall be continuous.

Second-round opponents Andrey Rublev of Russia and France’s Arthur Rinderknech wrapped themselves in ice towels during the changeovers, and Rinderknech fell to the court from exhaustion after a 37-shot rally.

Rublev, who entering Wednesday was 1-19 after dropping the first two sets in best-of-5 matches, completed the second 0-2 comeback of his career with a 4-6, 5-7, 6-1, 6-2, 6-2 win.

ESPN Stats & Information, The Associated Press and Reuters contributed to this report.