Casper Ruud's Australian Open tune-up has begun impressively, while Petra Kvitova has sealed a first United Cup victory for the Czech Republic by beating Germany's Laura Siegemund in Sydney.
Kvitova's 6-4 6-2 win on Sunday morning gave her country an unassailable 3-0 lead, securing the tie after star German Alexander Zverev was upset by Jiri Lehecka in his comeback from injury a day earlier.
Germany won the second men's singles rubber and the mixed doubles, but the Czechs still walked away with the 3-2 victory.
The Czechs' win moves them to 1-1 after losing their opening tie of the new mixed teams event 4-1 to the United States, who can secure their passage to the semi-finals with victory over Germany from Monday.
Kvitova, ranked 16 but a former world No.2, was tested by the world No.177.
But the left-hander swung freely to break at 5-4 in the first set and then rifled another winning return past the German to set-up a 2-0 advantage in the second set before eventually prevailing in one hour, 50 minutes.
In Brisbane, world No.3 Ruud fought to keep Norway alive, beating Brazil's Thiago Monteiro 6-3 6-2.
After an ankle injury kept him out of last year's Australian Open, Ruud powered to the finals of the French and US Opens to peak at No.2 in the world.
"It's always refreshing waking up on January 1. I always feel very motivated coming down here to Australia," he said.
"Last year was a bit unfortunate, so I'm very eager to have a good start to the season and this is the perfect way to start."
However, Brazil went on to win the tie 4-1, with Laura Pigossi beating Norway's Ulrikke Eikeri 6-3 6-4 in the women's singles rubber, and Brazil also winning the mixed doubles.
The result improved Brazil's overall record to 1-1, with Italy (1-0) able to secure passage if they beat Norway in the final Brisbane leg.
Bulgaria won their tie against Belgium 3-2 after triumphing in a pulsating mixed doubles contest.
World No.29 Elise Mertens gave Belgium a 2-1 lead in the tie after producing a stunning third set in her 6-4 3-6 6-0 win over Gergana Topalova.
But world No.196 Dimitar Kuzmanov levelled it up at 2-2 with a dominant 6-2 6-0 win over world No.129 Zizou Bergs.
Belgium were on track for victory after Mertens and David Goffin raced through the opening set of the mixed doubles, but Bulgaria's pairing of Isabella Shinikova and Alexandar Lazarov fought back to win 1-6 7-6 (7-5) 10-6 (match tiebreak).
Meanwhile, Poland and Croatia have both won their ties to stay in the hunt to take out their groups.
Hubert Hurcakz got the ball rolling for the Poles with a 7-6 (10-8) 4-6 6-3 win over Kazakhstan's Alexander Bublik before Magda Linette gave her team an unassailable 3-1 lead with a 6-2 6-1 victory over Zhibek Kulambayeva.
Hurcakz and Iga Swiatek won the doubles for a 4-1 win. Poland now face Switzerland for group supremacy.
Petra Martic got the job done in the first rubber of the night for Croatia, downing Argentina's Nadia Podoroska 6-2 4-6 6-1 to give her side a 3-0 advantage. Croatia went on to inflict Argentina's second 5-0 loss after already being whitewashed by France.
