(CNN) -- Twenty-fifth seed Stanislas Wawrinka of Switzerland survived a two-tiebreaker match against fourth seed Andy Murray of Great Britain to win 6-7(3-7), 7-6(7-4), 6-3, 6-3 at the U.S. Open.
Wawrinka's win on Sunday sets him up for a quarterfinal matchup against Sam Querrey.
Top seed and world number two Rafael Nadal of Spain handily beat Frenchman Gilles Simon 6-4, 6-4, 6-2. Nadal will face fellow Spaniard Feliciano Lopez, seeded 23rd, who was leading Sergiy Stakhovsky 6-3, 4-0 when the Ukrainian retired from the match.
Also continuing the dominance of Spanish men was Fernando Verdasco with a superb four-set third round victory over Argentine David Nalbandian.
The eighth seed Verdasco overcame a blip in the second set to go through 6-2, 3-6, 6-3, 6-2, one of seven Spanish players still left in the top half of the draw.
Verdasco will play compatriot David Ferrer for a place in the quarterfinals.
Ferrer, seeded 10th, secured his place in the last 16 with a 7-6, 6-2, 6-2 success over another Spaniard, Daniel Gimeno-Traver.
Meanwhile, Sam Querrey, the youngest player at 22 still left in the men's draw, continues to keep American hopes alive with a superb 6-3, 6-4, 6-4 victory over Nicolas Almagro of Spain.
And John Isner will be hoping to join compatriot Querrey in the next round when he faces Mikhail Youzhny in the evening session.