WIMBLEDON, England — Cori Gauff stood near the net watching a lob from Polona Hercog sail over her head and across the shadows at Centre Court early Friday evening.
“Please go out, please,” Gauff said later, describing her thoughts.
The 15,000 spectators in the stands — most of them newly minted Gauff supporters — were probably thinking the same thing.
If the lob went in, it would be a winner for Hercog. If it went out, another milestone would belong to the 15-year-old who has, over the past five days, earned scores of fans not only at this tournament but worldwide.
The ball landed long, setting off an immediate wave of cheers that shook the hallowed court as the long-limbed Gauff jumped up and down in delight.
“I was like, ‘Wow, I can’t believe it, it’s been one long match!” she said later. “It’s finally over!”
Gauff had done the improbable yet again, beating a tour veteran at Wimbledon. This time she did it after losing the first set and falling behind by 2-5 in the second, when her opponent reached the first of two match points that would not be converted.
The final score: 3-6, 7-6 (7), 7-5, in 2 hours 47 minutes.
Suddenly, surprisingly, Gauff, also known as Coco, had barged her way into the round of 16 at Wimbledon. She is the youngest woman to reach the second week of a Grand Slam tournament since 1991, when a 15-year-old Jennifer Capriati made it to the Wimbledon semifinals.
Gauff has left fans at this tournament, and indeed across Britain and back home in the United States, in her thrall. Call it Coco-mania.
Gauff’s other victories this week — against Venus Williams, one of her idols, and the Slovakian veteran Magdalena Rybarikova — had set the stage for the excitement surrounding Friday’s match.
As is now fairly well known, Gauff had not expected to be at Wimbledon this year. Ranked No. 313 in the world, she came only after receiving a last-minute wild card into the qualifying tournament, which she marched through without losing a set.
By Friday, she was Wimbledon’s headline act. Tournament organizers placed Novak Djokovic, the defending men’s singles champion, on the No. 1 Court, the second largest, while Gauff got the main stage against the 60th-ranked Hercog.
Gauff had played her first two matches on the No. 1 Court, and for a long while Friday it seemed that the bigger platform might be too much.
It hit her at the start, Gauff said later. Her description of the feeling: “Wow, I’m really on Centre Court. One of the most sacred courts in the world.”
For the first time in the tournament, Gauff seemed to play like the inexperienced teen that she is. She struggled for her range, spraying balls long and wide.
Hercog, a 28-year-old Slovenian, went all out on her own groundstrokes and homed in on Gauff’s forehand, which has a bigger swing than her compact backhand and is more prone to errors.
“I felt like I had to go bigger, because she was hitting so many forehand winners,” Gauff said. “I knew that I had to hit bigger. I think I was trying to hit too big, to a point where I was missing a lot.”
The first set went by quickly, and the second initially looked like more of the same. Hercog raced to a 5-2 lead and was poised for the win. Serving to stay alive, Gauff saved a match point with a slicing, down-the-line backhand that peeled off the sideline for a winner.
Hercog served in the next game and gained another match point. This time she double-faulted. From then on, this contest was a battle of wills.
In the tiebreaker, Gauff fell behind again. But she began opening her shoulders and hitting with more power, while also reining in errors. When she took the tiebreaker by ending a 32-shot rally with a forehand winner, the crowd went nuts.
“We Brits love our fairy tales, and this is a fairy tale!” a BBC announcer said, surely aware that the match was drawing a large audience. Gauff’s match on Wednesday had been the most watched in Britain from this year’s tournament.
Gauff took an early lead against Hercog in the third set but lost it. With her opponent gaining confidence, Gauff responded by cranking up her power again. She held her last two service games without losing a point.
Then, with Hercog serving to stay in the match and the crowd cheering wildly, came the final breathless, side-to-side rally. The 19th shot was Hercog’s lob. When Gauff watched it sail long, the grounds at the All England Club thundered — from Centre Court to a packed crowd watching on the video screen at Henman Hill.
In the news conference afterward, Gauff flashed a mix of preternatural calm and teenage giddiness. Before any of the reporters could get off a question, she smiled broadly and said she had an announcement.
“I know this is off topic,” she said, “but I wanted to say, ‘Please stream “Erys” by Jaden Smith.’ His album dropped yesterday.”
Gauff was all business for a while after that. She adroitly analyzed her match, thanked her coaches and explained how she had practiced her slice groundstrokes before Wimbledon, which rewards low, skidding sliced balls.
“I’m definitely learning from each match,” Gauff said. “Seeing that crowd and hearing how they react sometimes in the middle of the point, they get excited. I’m just getting a little bit of experience match by match.”
Then she lapsed back into being a teenager. Told that images of her mother dancing during the match were going viral on social media, Gauff showed more excitement than she had at any other point in the media room.
“Please tell me she’s a meme!” she said giddily. “I’m so excited to go on Instagram!”