Teenager Coco Gauff ended the grand-slam comeback of Caroline Wozniacki to reach the quarter-finals of the US Open.The 19-year-old came from a break down in the first and third sets to win both and complete a 6-3 3-6 6-1 victory.Wozniacki's return has been one of the stories of New York this year, having come out of retirement after more than three years and two children later.The 33-year-old former world No 1 has looked as though she has never been away, but a fired-up Gauff proved just too strong in the deciding set.Romanian Sorana Cirstea reached the quarter-finals of a grand slam for the first time in 14 years on Sunday after upsetting 15th seed Belinda Bencic 6-3 6-3 at the US Open.Making her 59th Grand Slam main draw appearance and 15th at the US Open, the 33-year-old Romanian's only other quarter-final appearance was at the 2009 French Open.Cirstea becomes the oldest woman to reach the last eight at the US Open for the first time.The upset is just the latest in what has been a remarkable run for the Cirstea, who had already delivered one of the big Flushing Meadows shocks taking out fourth seed and 2022 Wimbledon champion Elena Rybakina in the third.Next up for the Romanian is Czech 10th seed Karolina Muchova who advanced with a 6-3 5-7 6-1 win over China's Wang Xinyu.