Sebastian Korda was cruising and looked like he was about to win. He was ahead in the fifth-set tiebreak versus Hubert Hurkacz and he was up 7-3. But then he began nervous, and he made four errors in a row. He could have lost it right there. But all of a sudden, he locked in again, and knew that he could slam the ball at the right time. He did, and he won it, 3-6, 6-3, 6-2, 1-6, 7-6(7). He was finally overjoyed.

“Maybe nerves got a little bit to me,” Korda said. “He stopped missing a little bit more. Came closer to the line. And I made some easy mistakes, and he took advantage of that.”

But not for long. Over the past five years, the American could look pretty good, but then he collapsed a lot. His father, Petr, won the 1998 Australian Open, and he could run all day. Plus, he could move forward, even into the net. But Sebastian needs more time. His forehand and backhand are powerful, but his serve, his return and net game, aren’t quite good enough. But he worked hard, mentally, and now, he is much more mature.

“It was difficult but I’m very happy with the way I kind of just stayed down, kept going through it,” he said. “Throughout this whole year, I haven’t had one negative thought, whether it’s waiting for transportation to go to the courts, whether it’s eating lunch, whether it’s doing anything. That’s one of the biggest things is just having a new motto of, positive energy is more positive than negative energy. As soon as you get something negative, it can take you the opposite direction. Anything that happens, just thinking in the most positive possible way, just going forward.”

Now he is in the quarters at a Grand Slam for the first time. Obviously, he is confident. But in the second weeks of the Slams, you have to face the talented players. He realizes he would back off when the match is tight.

“I think I’ve had a tough match with Rafa [Nadal], serving for it a couple times. Match point with [Novak] Djokovic. I think that really helped me, especially in the last match with Medvedev, closing out that tiebreaker,” Korda said. “Then today as well. I think all those little moments that I’ve gone through, learning from them, staying patient, staying positive, going through the process I think have really helped me going forward.”

Korda will play Karen Khachanov, a player who showed a lot of potential a few years ago. The last time they played the Russian beat Korda 10-8 in the fifth set at Wimbledon. This will be a tossup.

How about Stefanos Tsitsipas, who advanced after he survived Jannik Sinner 6-4, 6-4, 3-6, 4-6, 6-3. He could have lost, but he kept on trunking. He was composed.

It was a bit of a stunner when Jiri Lehecka upset Felix Auger-Aliassime in four sets. Apparently, Lehecka is super steady, and he will snap the ball when he had to.

Jelena Ostapenko won 2018 Roland Garros and then she almost disappeared. She is a huge server, from both sides, and she goes for it immediately. But she can hit it way too long. Time and time again.

She just beat Coco Gauff and, as she said, she finally has became more thoughtful, on the court.

“My life changed a lot [after winning Roland Garros], so I needed a few years to really get used to what happened because I was really young,” Ostapenko said. “I was 19 and then turned 20. I always knew and believed in my game. If I play well, I can beat almost anyone. I was trying to work more on my consistency, especially in the preseason. Yeah, just to step on the court and play my game.”

In the quarters, Ostapenko will play Wimbledon champ Elena Rybakina, who is 2-0 over the Latvian. Ostapenko is the favorite, but not by much.

Once again, Jessica Pegula won a fine match, advancing over Barbora Krejcikova. She made few errors, and she also nailed her forehand and backhand. She has a real chance to reach into the semis for the first time at the Slams.

“It feels like there’s still a long ways to go, to be honest,” Pegula said. “I look at the draw you have Rybakina who won Wimbledon last year, you have Vika [Azarenka] who does really well here, Caroline [Garcia] won the [ATP] championships. It doesn’t really feel like I’m the highest left, even though I guess that’s a cool stat.”

She will face against Azarenka, who won this tournament twice but that is a long time ago. They have met four times and have split. Azarenka is a huge hitter from both sides, but her serves can be spotty. Still, she is very confident.

“I’m so happy I was able to manage it. At the beginning of the year there were a couple of very close matches that didn’t turn my way, so I’m very happy that I took my chances,” Azarenka said.