Taylor Fritz withstood an early assault from Canadian Denis Shapovalov to earn a Qatar Open quarter-final place 5-7, 6-3, 7-5 on Thursday.
The win was the second in two days for the American who had knocked out David Goffin in the second round while saving match points.
Shapovalov unleashed a run of 24 consecutive winning points in the first set to take the early lead but could not hold off his North American rival.
Fritz won his first match in the series after losing the first three, including at last year’s US Open in a five-setter.
“It was mentally a huge victory,” the winner said. “After our last match I didn’t want to lose again, so I pushed harder.
“I’ve had a lot of court time and close wins, coming through under pressure, I want to keep it going.”
The player who will meet the winner from Roger Federer and Nikoloz Basilashvili, added:
“I had to play myself into the match. I was holding pretty easily. I was lucky when the chances came (to break), I was able to take it.”
Fritz missed on two match points before finally coming good.