19 double faults and 60 unforced mistakes led to a 6-3, 4-6, 6-3 fourth round loss for third-ranked Gauff, as per AFP.
With the 20-year-old’s exit, Serena Williams is still the only female player who has won the US Open since 2014.
“I lost in the first round the last two years and now to be making the quarter-finals is pretty insane,” said American Navarro who will face Spain’s Paula Badosa for a place in the semi-finals.
“This is the city I was born in and it feels so special to be playing here. Coco is an amazing player. I have a ton of respect for her and I know she’s going to come back here and win this thing again.”
Gauff’s defeat dealt a further blow to the season’s last Grand Slam event, with the elimination of reigning champion Novak Djokovic in the third round, his earliest exit since 2006.
Alcaraz, a popular player who won in New York in 2022 and is currently the champion of the French Open and Wimbledon, was taken aback in the second round.
Navarro, who had beaten Gauff at Wimbledon in July, dominated right away on Sunday as well.
The 23-year-old broke for a 4-2 lead in the opening set and closed out the first game with a 27-shot rally in the ninth game.
With a break in the second set, Navarro extended her advantage to 4-3 when Gauff made her fourth double fault of the match.
But Gauff, who had trailed Elina Svitolina in her third round victory, rallied to win the next three games to even the match.
The champion’s temporary reprieve was short-lived, as she gave up three more double faults in the decider’s third game, giving away another vital break point.
Badosa, who was born in New York City as well, defeated Wang Yafan of China 6-1, 6-2 to advance to her maiden US Open quarterfinal.
The first two games lasted seventeen minutes each, despite the lopsided result. All eight of Badosa’s break points were saved.
“It was so humid I thought I was going to die,” said the 26-year-old. “I knew she was tough but I’m tougher.”