Carlos Alcaraz passed a tiebreak test on Thursday as the top seed squeezed into the Toronto Masters quarter-finals with a 3-6, 7-6 (7/2), 7-6 (7/3) victory over Hubert Hurkacz.
World number one Alcaraz was only just able to extend his win streak to 14 matches as he fended off a third-set offensive from his 15th-seeded Polish opponent.
Alcaraz needed five match points to advance over Hurkacz and flirted with disaster as he let a 5-2 lead in the final set slip into a second consecutive tiebreak.
"I was in trouble serving for the match - I don't know how I won," he said after winning his 19th Masters 1000 match from 21 played this season.
"I was fighting, there was a fire inside; this match was pretty tough.
"In the tough moments I told myself to keep fighting and go for it, play aggressively."
The Spaniard went from 5-2 to 5-6 in a heartbeat before pulling out victory.
"I was feeling bad and could not feel my shots. But I just stayed calm and tried to find the good feeling again," he said.
"Top players have to find the way to stay alive and end the match playing well."
Alcaraz will face either American 12th seed Tommy Paul or qualifier Marcus Giron in the last eight.
Elsewhere on Thursday, Andy Murray's tournament ended abruptly with the British veteran withdrawing injured shortly before his last 16 clash with Italy's Jannik Sinner.
"I can't play this evening," the 36-year-old said as he addressed fans on court.
"I feel like I've let the crowd down. I've rarely had this situation in my career. I feel terrible, this feels rubbish."
- Medvedev mastery -
Meanwhile second seeded-Daniil Medvedev's hardcourt mastery continued with a 6-4, 6-4 victory over Lorenzo Musetti.
Medvedev dispatched the number 19 Italian in 93 minutes with three breaks of serve, pushing his tour-leading number of hardcourt match wins to 31 with just three defeats.
The 2021 Toronto champion is chasing his sixth title of 2023 and his fifth on hardcourt.
He will bid for the semi-finals against Alex de Minaur, who defeated eighth seed Taylor Fritz 7-6 (9/7), 4-6, 6-1.
There was disappointment, however, for third-seeded Casper Ruud, who came up just short in his bid to battle past Alejandro Davidovich Fokina, who pulled off an upset 7-6 (7/4), 4-6, 7-6 (7/4) win.
Medvedev said that despite the relatively straightforward score, blustery winds gave him some problems against Musetti.
"It was not easy to play, it was not the worst wind but it was changing from fast to slow," he said.
"You can't hit full power in those conditions and you don't know what to expect. It was not easy for either of us, but I did enough to win. I missed some shots today, but I had quite a good level and I'm happy about it."
Norway's Ruud served for victory against Davidovich Fokina at 5-4 in the third set, but dropped his serve in the clutch moment.
The Spaniard took the set into a tiebreaker and finished off the upset after three hours on court.
"I kept very focused on every point when he served for it," Davidovich Fokina said. "I told myself to be there, don't give up."
Ruud saved two match points in the tiebreaker before succumbing to an opponent who finished with 49 winners and 56 unforced errors.
The match was paused for an hour and three-quarter hours in the second set because of rain.
Davidovich Fokina booked a quarter-final clash with American Mackenzie McDonald, who beat Canada's Milos Raonic 6-3, 6-3.
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