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Popyrin, who is the defending champion but seeded No.18 for the tournament in 2025, extended his winning streak to nine matches in Canada.

He stunned former world No.1 Daniil Medvedev in the third round, and is now into his first hard-court quarter-final at any level since his stunning run to the title 12 months ago.

The 25-year-old Aussie missed plenty of opportunities in the first set and dominated with 11 break points, but he couldn't convert any as Rune lucked his way through it to take the match lead.

But Popyrin blasted past Rune in the second and third sets, upping his aggression with some sensational hitting, firing 30 winners past the Dane on his way to winning in just shy of two hours and four minutes.

Popyrin said it meant a lot to be in the last eight having started the week with low expectations.

"I started the week low on confidence, but my game was always there I just needed the mental side to get to grasp," he said after beating Rune.

"This week I kind of just let go of all the pressure that I had, and you know, it's working out for me, which is good.

On his failure to take his chances in the first set, Popyrin didn't hold back.

"I was pissed," he said. "The first 20 seconds to a minute I was pissed, but when I came out to return again, it kind of felt like I was in control of the match, so I just told myself to keep doing what you're doing, and eventually he'll ... well, you don't save 11 break points against me in a row.

"I just said to play aggressive on the next break point that I got and I did that and from then on I felt comfortable."

Next up for the Australian is No.1 seed Alexander Zverev, who will be fresh after his clash with Francisco Cerundolo was cut short after just one set because of an injury to the Argentian, who was 4-6 0-1 down when he decided to throw in the towel.