NEW YORK -- This is Coco Gauff ‘s fifth year as a regular on the Hologic WTA Tour. It’s easy to forget that the 19-year-old is still very much a work in progress. She’s likened the process to building a house.

“Still building,” Gauff said on Sunday after defeating Caroline Wozniacki. “I think I could have handled my service games a lot better. Still picking the right shots, in that second set I had a lot of short balls, just errors. I think I need to go for bigger targets.”

Suddenly, the biggest of the targets remaining this season looms within reach. On Tuesday, Gauff advanced to the US Open semifinals with a dominant 6-0, 6-2 victory over Jelena Ostapenko, extending her winning streak to 10 matches. 

US Open 2023: Draw | Order of play | Scores | 411

It was over in 68 minutes and was the most lopsided win in a Grand Slam over her career. It’s the second major semifinal for the No.6 seed after playing last year’s final at Roland Garros. Ostapenko managed to hold serve only once.

On a day when the temperature soared past 90, Gauff continued her blazing summer run through North America’s hardcourts. She’s now won 16 of 17 matches in a span of 35 days. Note to historians: Gauff is the first American teenager to reach the semifinals here since Serena Williams did it in 2001.

Her next opponent will be No.10 seed Karolina Muchova. It will be a rematch of the Cincinnati from two weeks ago, which Gauff won. 

Muchova bests Cirstea to make first US Open semifinal

It was a sweet win for Gauff, who lost to Ostapenko in the fourth round of this year’s Australian Open.

“I’m so happy,” she said in her on-court interview. “Last year I lost in the quarterfinals. I’m happy and ready to get back to work on the next one

“Honestly I didn’t feel comfortable at all during the match – even on the match points. It’s tough against her, because you can’t really be aggressive.”

Ostapenko has always been a hit-or-miss, all-or-nothing player.

The misses have come often for the 26-year-old Latvian, but, oh, those direct hits have been glorious. She was still a teenager when she won the 2017 French Open, just 20 when she reached the Wimbledon semifinals.

That was more than five years ago. On Tuesday, she had a chance to return to that elite level.

In her second-round win over Elina Avanesyan, Ostapenko was credited (if that’s the word) with an astonishing 80 unforced errors. In the end, however, she was a winner. Against Gauff, Ostapenko committed four unforced errors -- in the first game alone.

The American went on to pitch a nearly perfect game, winning 24 of 31 points and closing the first set out in 20 minutes. The last point was an artful drop shot. Factoring in her last set against Caroline Wozniacki, Gauff had won 12 consecutive games on Ashe. 

For the record, Ostapenko had 13 unforced errors.

The second set began much the same. Gauff broke her serve for the fourth straight time, ending it with another drop shot. Ostapenko finally broke through with a service break when Gauff sent a too-flat forehand into the net.

"Today was the best match I've played [in the tournament], for sure," Gauff said. "Even though it wasn't how I like to play, against her it's so hard to be the aggressor sometimes. The way decision-making is probably the best I've had, and I feel really confident in all my strokes."

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Ostapenko had four game points to convert her first service win -- and Gauff fought off each one. A backhand crosscourt winner gave her a 2-1 lead and left Ostapenko still looking for a winning service. 

There was minor opening when Ostapenko forged a break point, but two more errors gave Gauff a 3-1 advantage. Finally, 49 minutes into the match, Ostapenko held serve for the first time.

Ostapenko had Gauff in a love-30 hole, but couldn’t level the set. Despite getting second serves, she drilled two forehands long before another error gave Gauff a 4-2 lead. A forehand flip into the net put Gauff in a position to serve for the match.

In the end, Ostapenko had 36 unforced errors -- 22 more than Gauff, who refused to be drawn into a slugfest.

"Right now I feel emotionally fresh, which I think was the problem in the past in Grand Slams, I would emotionally be drained," Gauff said. 

"I think this is one of the harder runs I've had to the quarterfinal stage. Obviously never got to semis, but I don't know, I just feel so fresh, to be honest. I don't know if it's because I've been tricking myself or maybe when this is over I'm going to hit a wall. But I'm really proud of how I'm able to get through these matches."

Five best points from Gauff's win vs. Muchova in Cincinnati final