American wildcard James Blake set up a quarter-final with Andre Agassi after sweeping aside Tommy Robredo 4-6 7-5 6-2 6-3 at the US Open.
The New Yorker looked out of sorts in the early stages as the Spanish 19th seed took the opening set before racing to a 5-2 lead in the second.
But Blake suddenly responded, winning five games in a row to level the match.
The American then overpowered a wilting Robredo with his athletic play to comfortably take the next two sets.
Blake, who has recovered from a year of illness and injury, will meet Agassi on Wednesday.
"A year ago I would never have believed that I would be playing in the quarter-finals of the US Open against a legend like Agassi," said the 25-year-old.
"Robredo was playing great and I just had to scrap my way back into it. I have no idea how I did it.
"But when you are down here it doesn't seem like you are down because I have so many fans cheering for me."
Guillermo Coria saw off Nicolas Massu 6-4 2-6 6-7 (7-5) 6-2 6-2 in an ill-tempered encounter on Louis Armstrong Court.
The Argentine eighth seed took the opening set but Massu responded in the second to level the match.
Both players traded aggressive strokes - and occasionally words - from the baseline as Massu clinched the third set tie-break to move ahead.
But Coria regained his form to wrap up the next two sets and book his place in the quarter-finals at Flushing Meadows.
The quality of tennis in the four-and-a-half hour marathon was overshadowed by the heated verbal sparring.
Tournament official Mike Morrissey had to make a plea for calm in the fifth set after both players exchanged insults from their chairs during the changeover.
Massu commented on the argument: "I don't have a problem with Guillermo.
"I don't know what happened to him today. I was surprised what he did. What can I do?"
Coria will next face unseeded American Robby Ginepri, who outlasted French teenager Richard Gasquet 6-3, 3-6, 6-7 (8-10), 6-4, 6-0 in a marathon match.
Ginepri took the opening set in just 23 minutes after breaking early and dominating 19-year-old Gasquet, who needed treatment for tendinitis in his right arm.
Gasquet broke in the fourth game of the second set and survived four set points to win the third on a tie-break.
With Gasquet needing more treatment for his arm and struggling with a stomach strain, Ginepri regained the iniative in the fourth set and ran away with the decider in just 20 minutes to reach his first Grand Slam quarter-final.