Coco Gauff turned things around after being a set down and beat Elina Svitolina 3-6, 6-3, 6-3 in the U.S. Open's third round on Friday, extending the 20-year-old American's defence of her first Grand Slam title.

The third-seeded Gauff made mistake after mistake in the first set at Arthur Ashe Stadium and dropped its last 11 points against the 27th-seeded Svitolina, a three-time major semifinalist.

"She's a fighter," Gauff said from New York. "I knew I had to play my best."

But Gauff managed to reel off nine of 11 games in one stretch and won despite losing the opening set, something she did three times en route to winning the 2023 trophy at the U.S. Open, including in the final against Aryna Sabalenka.

The secret this time?

"I tried to be more aggressive on my forehand side," Gauff said, "and tried to make less errors on the backhand."

Sounds simple enough, right?

By the conclusion of one set, Gauff's totals were 16 unforced errors — nine on backhands — and just seven winners. She put only 45 per cent of her first serves in. She went 0-for-3 on break points. She allowed Svitolina to claim 19 of the 28 points that lasted more than four strokes.

All of those numbers got better across the last two sets. And something else changed, at the behest of her coaches: Gauff got the partisan crowd more involved.

"My team was kind of like telling me that (the fans) were on the edge of their seats," Gauff explained. "So I said, 'OK, I need to erupt so you guys can erupt."'

This comeback ends a five-match losing streak for Gauff against opponents ranked in the top 50 and might be just what she needs to move past a recent slump that saw her win just five of her previous nine matches.

Faces Navarro or Kostyuk on Sunday

Such a contrast to a year ago, when Gauff won 18 of 19, and 12 in a row, along the way to two tuneup titles on hard courts and then the championship at the U.S. Open that made her the first U.S. teenager to triumph at Flushing Meadows since Serena Williams in 1999.

On Sunday, Gauff will play for a berth in the quarterfinals. That will come against the winner of Friday's later match between No. 13 Emma Navarro of the U.S., who beat Gauff in Wimbledon's fourth round last month, and No. 19 Marta Kostyuk of Ukraine.

Everything began to change for Gauff on Friday after one hour 10 minutes, when Gauff broke to lead 4-2 in the second set, smacking a cross-court forehand winner. She celebrated with a yell of "Come on!" and raised her left hand to wiggle her fingers and ask the crowd to get louder.

Soon that set belonged to Gauff, who closed it with a 94 mph ace, shook a fist and shouted.

In the third, with UConn women's basketball stars Paige Bueckers and Azzi Fudd sitting in her guest box at Ashe, Gauff broke right away, then held to go up 2-0 with the help of one 38-stroke point that she took when Svitolina sent a backhand wide.

Soon it was 5-1 for Gauff, whose only late wobble came when she served for the match at 5-2. She wasted three match points and got broken there. But Gauff broke right back to close things out.

WATCH | Canada's Gabriel Diallo through to 3rd round:

Canadian qualifier Diallo advances to 3rd round of U.S. Open with another upset win

After earning his first ever Grand Slam win on Tuesday, Montreal's Gabriel Diallo defeats 24th seed Arthur Fils of France 7-5, 6-7 (3), 6-4, 6-4 in the second round of the U.S. Open.

Zheng scores swift win over Niemeier

China's Zheng Qinwen shook off slow starts in the opening two rounds of the U.S. Open and took down unseeded German Jule Niemeier 6-2, 6-1.

The Olympic gold medallist and seventh seed fired off eight aces and seized five break points on the Grandstand hard court in her first straight-sets victory of the year's final major.

Niemeier, nursing a foot injury, committed five double faults and held serve in just three games of the match that wrapped up quickly in an hour and 21 minutes.

Zheng was sharp from the start, blasting two aces to open the second game and breaking Niemeier's serve in the fifth to seize control of the match and energize scores of Chinese chanting "jiayou" from the stands.

A cross-court forehand blast captured a second service break for the 2024 Australian Open runner-up as Niemeier's forehand return found the net.

Zheng grabbed seven straight points to open the second set and cruised to the win, avenging a third-round loss to the German at her first U.S. Open in 2022 and setting up a fourth-round clash with either Donna Vekic or Peyton Stearns, who play later on Friday.