INDIAN WELLS, Calif. -- In her last singles match as a teenager, Coco Gauff was mature beyond her years at the BNP Paribas Open.

Faced with nine break points in her first three service games, Gauff saved each and every one of them and went on to a 6-2, 7-6 (5) victory over Lucia Bronzetti.

The No.3-seeded Gauff will meet No.24 seed Elise Mertens for a berth in the quarterfinals. Mertens advanced to the Indian Wells Round of 16 for the first time by defeating former No.1 Naomi Osaka 7-5, 6-4. Gauff is undefeated against the Belgian, winning all three of their previous matches, including a three-set win last fall en route to the US Open title.

That match will be played on Wednesday, Gauff’s 20th birthday.

Thus, the book can be closed on the teenage triumphs of the 2023 US Open champion. Since the WTA 1000 format was introduced in 2009, no teenager has posted as many trips to the Round of 16 as Gauff (16), or won as many matches (51).

What present does she want for her birthday?

“I don’t know,” Gauff said in her on-court interview. “I’m just happy to be alive. I’m really happy to see 20.”

And then she laughed and revised that statement.

“I don’t want to jinx it,” she said, “Hopefully I’ll see 20.”

Ultimately Gauff saved 10 of 11 break point opportunities forged by Bronzetti.

Bronzetti was attempting to win three straight WTA 1000 matches for the first time in her career and is now 0-5 against Top 10 opponents.

Gauff got off to a blazing start this year, winning the title in Auckland and reaching the semifinals at the Australian Open. Riding a 10-0 record, she ran into eventual champion Aryna Sabalenka, losing 7-6 (2), 6-4. The Middle East swing resulted in a 2-2 mark, with losses to Katerina Siniakova and Anna Kalinskaya.

Here in the desert, Gauff got off to a slow start in her first match, against Clara Burel. Down a set and a break, Gauff eventually forced a third set -- and promptly fell into a 0-4 hole. She rallied famously and was triumphant in a tiebreaker.

The trend continued against Bronzetti, a 25-year-old Italian who is ranked No.53. Under duress, Gauf tended to move forward and finished a number of points with thumping overheads. After saving five break points in the fifth game alone, Gauff broke back -- at love -- to take a decisive 4-2 lead. She converted her fourth set point when a Bronzetti backhand found the net.

With Bronzetti serving at 2-3 in the second, Gauff forged a pair of break points. She grabbed the first one available when Bronzetti struck an errant forehand. But, for the first time in the match, Bronzetti returned the favor and thrust the set back on serve.

It was decided in the tiebreaker. Gauff hit a successful drop shot to draw even at 5-all before Bronzetti dumped a backhand into the net and Gauff smoked one last unreturnable serve.