Sydney, Felix Auger-Aliassime fired Canada into the semi-finals of ATP Cup on Thursday, upsetting World No. 3 Alexander Zverev 6-4, 4-6, 6-3 to earn the first Top 5 win of his career.

Following Great Britain's 2-1 triumph against the United States earlier on Qudos Bank Arena, Canada knew victory against Germany would seal a semi-final spot.

With the pressure on, Auger-Aliassime backed up Denis Shapovalov's victory over Jan-Lennard Struff by showing great resilience against Zverev in a statement win. With his victory, Canada has clinched the Group C tie 2-0 and will play reigning champion Russia on Saturday in Sydney.

"It feels good to beat Zverev," Auger-Aliassime said in his on-court interview. "I played a great match. He is a great player and he has beaten me a couple of times before, so I am happy I was able to get the job done today, especially for the team. We started off on a tough day a couple of days ago, so to finish off strong and be through to the semis is special. The atmosphere was great at the end, that is what we play for."

In an entertaining match, the 21-year-old recovered from squandering four break points at 3-3 in the second set, hitting with great power and depth in the third set to triumph after two hours and 32 minutes.

The World No. 12, who kept Canada's ATP Cup bid alive with his singles victory against Cameron Norrie on Tuesday, was strong on serve throughout, winning 76 per cent (41/54) of points behind his first delivery. The 21-year-old maintained a high and consistent level in a tense deciding set, breaking in the seventh game as he reduced his ATP Head2Head series deficit to 2-4 against the German.

It is the first time Canada has reached the last four at the 16-team event. In the other semi-final, Poland will play Spain on Friday.

Earlier, Shapovalov boosted Canada's ATP Cup semi-final hopes, overcoming Struff 7-6(5), 4-6, 6-3.

Shapovalov, who is making his third ATP Cup appearance, gave Canada the perfect start as he bounced back from his singles defeat against Daniel Evans by dictating with his explosive groundstrokes against Struff. Shapovalov fired 41 winners to seal his win after two hours and 34 minutes.

"It is just great to be back and playing," Shapovalov said in his on-court interview. "We have got a great chance. There is a lot ahead of us, but we are fighting and we have been fighting every single match. Felix inspired us a lot in the previous tie and we are just trying to give all we have for Canada."

In a high-quality match, Shapovalov and Struff went toe-to-toe in brutal, heavy-hitting baseline exchanges. However, it was the World No. 14 who raised his level in the third set, saving all four break points he faced in the decider to give Canada the advantage. With victory, the 22-year-old has reduced his ATP Head2Head series deficit against the German to 3-5.

"I knew I had to fight every point," Shapovalov added. "I have had a tough record against Struffi, he is a tough player to play and he always brings it against me. I think the level was really, really high so it was a great win to get."