NEW YORK — World No. 6 Jessica Pegula reached her first Grand Slam final after completing a stunning comeback to defeat Karolina Muchova 1-6, 6-4, 6-2 in the US Open semifinals on Thursday. The 30-year-old Buffalo native trailed 6-1, 2-0 before rallied for her 15th victory in her last 16 matches.

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Pegula is the oldest American woman in the Open Era to reach a first Grand Slam final. She is the third American woman 30 or older to reach a US Open final, after Serena Williams and Martina Navratilova.

After an injury-ridden start to her season that saw her miss four WTA 1000 tournaments and the French Open, Pegula entered the summer hardcourt season ranked No. 20 on the PIF Race to the WTA Finals and could leave New York City ranked No. 3. She has breezed through the hardcourt summer, capturing her third WTA 1000 title in Toronto, finishing runner-up in Cincinnati and securing a spot in the US Open final.

Pegula is the fourth player in the Open Era to reach the finals of the Canada, Cincinnati and US Open in a single season, after Rosie Casals (1970), Evonne Goolagong Cawley (1973) and Serena Williams (2013). It is the first time since 2002 that an American man and woman have reached the finals of a Grand Slam singles event.

Pegula will face world number two Aryna Sabalenka for the US Open title on Saturday. The match is a rematch of last month’s Cincinnati Open final, which Sabalenka won 6-3, 7-5.

The story of the tape: Pegula reached her first major semifinal after beating world number one Iga Swiatek to break her 0-6 drought in the Grand Slam quarterfinals. The 30-year-old American was reportedly the best player of the summer after winning 14 of her last 15 matches to win the title in Toronto and the final in Cincinnati.

Pegula looked set to build on that success early in the match, having first faced Muchova three weeks ago in Cincinnati, where Pegula won in three sets.

Muchova quickly out of the starting blocks: After trading holds to open the match, Pegula earned three break points when Muchova was serving at 1-1. Muchova dug in to save all three chances and from there the Czech turned the tide. After holding until 2-1, Muchova won eight straight points to break her lead and extend it to 4-1. She unleashed her attacking all-court game to keep Pegula off balance and demoralized the world No. 6 with spectacular shotmaking to race away the set after just 28 minutes.

Muchova extended her lead to 2-0 in the second set before Pegula stormed back, saving break point to keep it 2-1 and then breaking Muchova for the first time with a sinking return that the surging Czech couldn’t save.

As Pegula dug in at the baseline to extend the rallies, her fortunes began to change. She held off another break point, this time with a well-constructed nine-stroke baseline rally, to stay 3-2. Pegula continued her march to break Muchova in a 10-minute game after Muchova capitulated with back-to-back backhand errors.

Turning point: Muchova halted Pegula’s four-game streak with a quick break of service, then rallied from 0-30 down to level the score at 4-4. But rather than become discouraged, Pegula quickly held at love and then broke Muchova to force a deciding set. Muchova hit her third double fault of the match on set point to end the physical 55-minute set and send the partisan crowd into cheers.

Pegula rode her momentum straight to the finish. She broke Muchova for a 2-0 lead and fought off a break point with a forehand winner to extend her lead to 3-0. Muchova kept the pressure on again and earned a break point from 40-0 down at 3-1. But the tired Czech hit an inside-out forehand wide and Pegula held on for a 4-1 lead.

Muchova would hold out one last time. With Pegula serving at 4-2, the Czech fought back from a 40-0 deficit to earn a break point. She saved five game points before the American’s ill-timed drop shot ended up in the net. But Muchova hit a legal backhand and threw her racket in the air in frustration. Pegula held on and broke one last time to secure the resilient victory after 2 hours and 12 minutes.

Next: Pegula defeated world No. 1 Iga Swiatek in the quarterfinals and will now face No. 2 Sabalenka in a second consecutive final. Sabalenka leads the head-to-head 5-2.