Pakistan, Sept. 7 -- Aryna Sabalenka and Carlos Alcaraz look to take another step toward defending their US Open championships when they play Sunday for spots in the quarterfinals. The top-ranked Sabalenka leads off against Taylor Townsend at Arthur Ashe Stadium in their first career meeting. Alcaraz, seeded second behind Alexander Zverev and playing his first tournament back following a wrist injury, follows against No. 20 Tommy Paul.

Townsend and Paul are among the 10 Americans to reach the men's and women's round of 16. That is the most in the fourth round at any Grand Slam in nearly a quarter-century, dating to the 2002 U.S. Open, when there were 11.

The five US men - Paul, Ben Shelton, Learner Tien, Frances Tiafoe and Alex Michelse...