Felix Auger-Aliassime: "Beautiful night" in Turin came from riding wave of self-belief against Alexander Zverev

When Felix Auger-Aliassime found the self-belief when he needed it most to secure the fourth and final spot in the ATP Finals semifinals.

The Canadian advanced our of the Bjorn Borg Group with a 6-4,7-6(4) win over Alexander Zverev on what he said was a "beautiful night" in Turin, thanks to a steely nerve when it mattered. In a tense affair, Auger-Aliassime saved break points in the fifth and ninth games of the first set before striking for the only break of the match, and won the last four points in the second-set tiebreak.

Read more: Carlos Alcaraz dedicates ATP Year-End No. 1 trophy to team, fans in Turin

"When a match is high stakes, the mentality is crucial," he told Prakash Amritraj on Tennis Channel afterwards. "I think your biggest challenge is self-belief in these matches so you have to come in with the best belief. You know you're going to play a tough opponent, you know you're going to have to be decisive when you need to, you're going to have to be smart, you're going to have to stay calm.

"There's going to be ups and downs, there was high tension in the second set, but at the end, I was able with a positive mindset ... beliving that my chance would come, and seize it."

Auger-Aliassime had reason to feel confident against Zverev. Though he trails the German in the overall head-to-head, he won their last meeting at the US Open. And after dropping his first three sets of the week, he secured a spot in the knockout rounds by winning his next four.

The belief came through in several big moments on serve, and not just in the games he faced break points. In the second set, he erased 15-40 on serve after failing to convert 15-40 on Zverev's serve in the previous game, and escaped a 3-3 service game at deuce after losing a 40-0 lead.

Read more: Felix Auger-Aliassime clinches “rollercoaster” comeback vs. Ben Shelton at ATP Finals

“It was a great first set. He was getting a few chances but I came up with big serves to save them,” Auger-Aliassime said. “The first set was very solid and the start of the second set was, too. I had a lot of chances.

"When that happens you need to focus on the present but you’re aware of missed opportunities, so the match got a little tense from that moment. But I was able to hold serve and in the ti-break it was tight 'til the end.”

Behind his 50th match win of the season, Auger-Aliassime becomes the second Canadian man to reach the year-end semifinals in singles after Milos Raonic in 2016.