What better place, then, for the 26-year-old to steady himself amid a turbulent year, one in which he has changed coaches, lost to unheralded opponents and tumbled down the world rankings? If only he could put together one good week, Tiafoe said in an interview, maybe he could reverse his fortunes.

Thursday marked the next step in what Tiafoe hopes is a turnaround, though it didn’t come easy. Before a lively, prime-time crowd at William H.G. FitzGerald Tennis Center in Rock Creek Park, Tiafoe defeated world No. 82 Aleksandar Kovacevic, 7-6 (7-3), 4-6, 6-3, in a round-of-16 match that lasted 2½ hours.

Leading 4-3 in the third set, Tiafoe earned a decisive break by handling a searing 129-mph serve from Kovacevic, the backward ballcap-wearing American, then winning the point with a passing forehand.

It was just the second of 11 break-point opportunities Tiafoe converted, but it was enough. He ended the match on his next service game with a clinching volley, then unleashed a roar that matched the adoring crowd.

“That 4-3 game was kind of everything,” Tiafoe said. “I upped my tendency there a little bit, started making some returns, made him play. … I hit an unbelievable shot to break there. After that I was able to open my shoulders and close the match out.”

Tiafoe arrived for the DC Open with a 16-16 record in 2024 that dropped the former top-10 player’s ranking to 29th and dented some of his trademark joy and confidence. His struggles prompted him to hire a new coach, David Witt, whose work with Venus Williams and Jessica Pegula drew Tiafoe.

Tiafoe also dealt with a medial collateral ligament strain during the grass-court season, though he acknowledged his challenges have been more mental than physical.

“The biggest thing I struggled with was the expectations part of it,” Tiafoe said earlier in the week. “I started playing much more safe and not as free, rather than just go out, enjoy the game, do what you do.”

Even in the middle of a difficult season, Tiafoe has talked openly about wanting to win his first DC Open title and adding his name to the list of champions that adorn the main stadium’s awning. He has never advanced past the quarterfinals here. But after two three-set wins to open the tournament, he will get an opportunity Friday.

“I kind of like that it was two tough matches that I won not playing incredibly well, just finding ways to win,” Tiafoe said. “That’s what it takes to be one of the better players in the world. That’s what I’ve been doing the last couple years.”

Tiafoe will next face world No. 8 Andrey Rublev, the tournament’s top seed. The 26-year-old Russian closed out Thursday’s slate of matches with a 7-6 (7-4), 6-4 victory over Frenchman Arthur Rinderknech.

Tiafoe was one of three top-30 American men to play round-of-16 matches under blistering heat Thursday.

In a midday match in the direct sun, world No. 23 Sebastian Korda outlasted Thanasi Kokkinakis, 6-7 (1-7), 7-5, 3-2. Korda earned a third-set break at 2-2, then led 40-0 on his next service game before Kokkinakis limped to the net, tossed his racket and retired because of cramping.

Kokkinakis, an Australian fan favorite ranked 91st, led early behind an overwhelming serve. In the first set, he won nearly 80 percent of his service points and fired two of his nine aces during the decisive tiebreaker. After Kokkinakis launched another ace to take a 5-2 lead in the second set, a dispirited Korda could manage only a shrug.

He quickly found some answers after the ensuing changeover. With Kokkinakis serving for the match at 5-3, Korda saved two match points with clutch defense, then earned his first break-point opportunity of the afternoon. A rare double fault by Kokkinakis gave Korda the game and prompted the hundreds of fans who braved the heat on the grandstand court to chant his name. The 24-year-old took the next three games and the second set.

“He was kind of slowing down a little bit with the pace of his serve [and] movement a little bit,” said Korda, who advances to a quarterfinal matchup Friday against Australian Jordan Thompson. “I just tried to keep hydrated, honestly. That was probably the key today.”

On the stadium court, world No. 14 Ben Shelton, the second seed in the men’s singles draw, prevailed in a nearly two-hour slugfest against fellow American Brandon Nakashima, 7-6 (7-5), 7-6 (7-4). The win came hours after the 21-year-old survived a three-set marathon in the round of 32 against qualifier Radu Albot that was pushed back by rain and ended at 1:46 a.m. Thursday.

“I was probably asleep at 4,” Shelton said. “ … Last night, had to deal with the humidity, playing in the middle of the night. Today was a quick turnaround and the heat. A lot of challenges thrown my way. It’s part of the sport. … I did a great job of recovering as best as I could and managing my energy out there.”

Shelton showcased a powerful serve that topped out at 146 mph. He fired his 14th and final ace on match point, then flexed on his way to greeting Nakashima at the net. He will make his first appearance in the DC Open quarterfinals Friday against Denis Shapovalov.

In the women’s draw, world No. 13 Ons Jabeur, the No. 4 seed, withdrew ahead of her round-of-16 match against 19-year-old D.C. native Robin Montgomery because of what she described as a recent right shoulder injury. (The Tunisian has also battled a balky knee for much of the year.)

Montgomery, a wild-card entrant in her DC Open debut, moves into the quarterfinals, in which she will meet Marie Bouzková.