Defending champ Rafael Nadal took full advantage of a fresh start, dominating Gilles Muller when their rain-delayed match resumed at the U.S. Open.

The second-ranked Spaniard was down a break, trailing 3-0 when play was stopped after 15 minutes Wednesday. He went on to win 7-6 (1), 6-1, 6-2 after they took the court Thursday, completing a fourth-round match that was supposed to start two days earlier.

The 68th-ranked Muller had not faced a seeded player in his first three matches. The lefty from Luxembourg reached the quarterfinals at the 2008 Open as a qualifier for his best performance at a Grand Slam, then was sidelined by a knee injury.

Nadal was coming off treatment for painful leg cramps during his post-match news conference Sunday, then was frustrated Wednesday that tournament officials tried to start play in less-than-ideal conditions.

He still faces a tough road to defend his title, potentially having to play four matches in four days.