Defending champion Rafael Nadal is on his way to the US Open quarterfinals.
The 76th-ranked Nalbandian went up a break in the fifth game and served for the first set at 5-4, but he double-faulted on break point. Then, at 3-all in the tiebreaker, Nalbandian double-faulted again, helping the second-seeded Nadal nose ahead.
Nalbandian broke to begin the third set, but Nadal broke right back to 1-1, then took an injury timeout after that game to have his right foot taped because of the blister.
"Every day is tougher and tougher," Nadal said in an on-court interview after the match.
He played far more cleanly and finished with only 18 unforced errors, 42 fewer than Nalbandian's total.
Muller is playing at Flushing Meadows for the first time since reaching the quarterfinals as a qualifier in 2008.
Based on reporting by the Associated Press.