A battle of youth, Nick Kyrgios took down Stefanos Tsitsipas in a thriller 7-6(7), 6-7(3), 7-6(5) at the ATP Cup in Brisbane Tuesday night.

Kyrgios, who missed the Sunday tie with a back injury, actually filled in for Aussie No. 1 Alex De Minaur who was a scratch due to an ab injury. And despite the Aussies having already qualified for the quarters, the team toppled Greece 3-0.

John Millman opened play edging Michail Pervolarakis 4-6, 6-1, 7-6(1). Then it was Kyrgios who reprised his tight win over Tsitsipas last summer in Washington.

“I served really well in big moments but the atmosphere was awesome. We’re carrying some momentum going to Sydney. It could have been easy to take your foot off the gas today. I thought both the Greeks showed up and I think they really wanted to win this tie, but I was happy we both got it done today,” said Kyrgios who once again showed he’s a big match player.

Tsitsipas finished the Cup 1-2.

“We had a difficult draw here in Brisbane, but we played with what we have,” Tsitsipas said. “Canada, Australia… Germany, one of the strongest nations in the game, playing against a small, tiny little nation like Greece, which has no history in tennis at all? You got to feel proud. We fought very hard and we wanted to prove to the rest of the world that [we] can play tennis anywhere in the world.”

Australia will now face Great Britain in the Thursday quarters in Sydney. The Brits won their group beating Moldova 3-0 in Sydney and after Belgium upended Grigor Dimitrov and Bulgaria 2-1. Dimitrov lost in singles and doubles.

In Perth, Russia advanced to the quarters with a 3-0 win over Norway while Italy took second blanking the struggling Americans 3-0.

“I think it was important for the guys to win as many matches as they can, so they are coming with full confidence after playing a lot of matches,” said Russian coach Marat Safin. “It’s beginning of the year, I think the guys are ready. They are pumped enough to do well in the final stage. I’m happy for them. I’m happy for myself. I think we are doing better each day.”

Back in Brisbane, Denis Shapovalov put a nail in Alexander Zverev’s final ATP Cup match hammering the fledgling star 6-2, 6-2 as Canada beat Germany 2-1 to keep their quarterfinal hopes alive.

“I’m really happy to get the win and hopefully we can go through. I feel like we’re definitely one of the top teams, and I feel like we definitely deserve to go to Sydney. Hopefully, if we do get that chance, we can do some really big damage,” Shapovalov said.

Zverev finished the Cup 0-3 with 31 double faults in three matches including 7 Tuesday.

“There’s a lot of things that I still need to improve, but it’s the start of the season,” Zverev said. “I need to find my rhythm.”

The last four spots in the ATP Cup quarterfinals will be determined on the final day of the round robin Wednesday.

Rafael Nadal will try to lead Spain in the last eight against Yoshihito Nishioka and Japan.

Novak Djokovic has already clinched, but they still face Chile. Djokovic will meet Cristian Garin.

Croatia and Marin Cilic can qualify with a win over Argentina.

France also faces South Africa and Georgia gets Uruguay.