NEW YORK — After two American favorites were upset early on Saturday, Coco Gauff snapped the ominous trend in the late afternoon, beating unseeded Cristina Bucsa 6-3, 6-4 in Arthur Ashe Stadium to advance to the fourth round of the US Open.

Playing each other for the first time in over three years, Bucsa jumped out to an early 3-1 lead in the first set, but Gauff broke back to tie it at 3-all. She then won the next three games to take the set, punctuated by a booming serve on set point that Bucsa couldn’t handle.

They each held serve through six games in the second set before Gauff broke for the 4-3 lead. The 28-year-old Spaniard broke back to level it, but Gauff took the final eight points to book her spot in the Round of 16 for the fifth consecutive year.

“It was way different playing in the day than at night,” Gauff said after the match. “I think I was decelerating a little bit, just because it’s a little bit faster. But once I was down that break, I just told myself I need to accelerate through my shots.

“She’s a tricky player. She can sometimes speed it up and slow it down. So it was tough for me to get a rhythm, but I’m just happy with how I fought through even when I wasn’t playing my best.”

Though the fourth seed made less than 50 percent of her first serves and double faulted six times, she won 20 of her 27 first-serve points. Her movement and defense were her hallmarks and gave her the edge, as per usual, converting four of nine break-point opportunities and winning 15 of 22 points at the net.

“I think I was finally feeling the ball good, maybe the last two games of the match,” she added, “so I started to rip a little bit more returns and come in a little bit more. When I feel like I’m not feeling the ball that well, I play defensive. I think today was mainly defense, honestly, in the first set because I just wasn’t feeling that great.

“Once I got my rhythm, then I was able to swing through a little bit more. And sometimes I need to just sacrifice some points just to hit through it, just to find my rhythm again. And I think that’s what I did.”

Gauff, who won her first WTA Tour Driven by Mercedes-Benz title of the year in Cincinnati last month, has now won nine matches in a row, the last eight of which have come in straight sets.

She’ll play either countrywoman Iva Jovic or Alexandra Eala for a spot in the quarterfinals. They’re playing the first night match in Arthur Ashe Stadium on Friday evening.