The two-time runner-up, ranked at a lowly 74 after an injury-hit campaign, eased to a 6-0, 6-2 win and will face second seed Angelique Kerber for a place in Saturday’s championship match.
Sevastova, playing in her first Grand Slam quarter-final, never recovered from falling and turning her right ankle in the second game of the opening set.
The 26-year-old was hobbled from that point on and the contest was over in just over an hour with the world number 48 having committed 30 unforced errors to the Dane’s five.
Wozniacki, the finalist in 2009 and 2014 and semi-finalist also in 2010 and 2011, sympathised with Sevastova after she spent almost three months out of the sport with a right ankle injury earlier this year.
“I feel really sorry for her as I have had that injury before,” said 26-year-old Wozniacki who will now return to the top 30 as a result of her surprise run in New York. I had to keep pushing her back and make her move.”
Sevastova, the Cinderella story of the US Open after she had retired in 2013, won just 12 points in the first set before she briefly rallied late in the match.
Even having her right ankle heavily strapped did nothing to improve her chances of becoming the first Latvian woman to reach the last-four at a Grand Slam. “It was tough, but what can I do? I tried my best. I don’t like to retire, but Caroline played great tennis. Even if I had no injury it would be tough to beat her,” said Sevastova.
Australian Open champion Kerber defeated Italy’s Roberta Vinci 7-5, 6-0 to reach her second semi-final in New York having also made the last four in 2011. Kerber holds a 7-5 career record over Wozniacki. The German second seed showed remarkable powers of resilience to retrieve three breaks of serve against Italian 33-year-old Vinci in the first set.
In a powerful demonstration of her title credentials, 28-year-old Kerber then wrapped up the second set of her quarter-final by allowing Vinci just five points on her serve. “It’s always tough to play Roberta, she always comes out to play great tennis,” said Kerber, who last made the semi-finals in 2011.