Alexander Zverev won his first match of the year as Germany beat Canada 2-1 in their ATP Cup group tie.
The 23-year-old, runner-up to Dominic Thiem in September’s US Open final, settled the tie with a 6-7 (5-7) 6-3 7-6 (7-4) win over Denis Shapovalov after Jan-Lennard Struff beat Milos Raonic.
Zverev said having his older brother, Mischa, as team captain had helped.
“All the players enjoy having him as captain and it’s just great to have him here,” he said.
Germany, who later lost the doubles rubber against Canada, will face Novak Djokovic’s Serbia on Thursday for a place in the semi-finals.
Italy became the first team to reach the last four as they beat France 2-1.
Fabio Fognini gave Italy an early lead with a 6-1 7-6 (7-2) win over Benoit Paire.
Matteo Berrettini, who beat US Open champion Thiem on Monday, then brushed aside Gael Monfils 6-4 6-2 to clinch victory in the tie before a French consolation win in the doubles.
“It’s a great team, great guys. We are enjoying on court, but off court as well,” Berrettini said.
“I think when you’re playing for your country, for your team, it’s something special.”
Russia will also qualify for the semi-finals if they beat Japan later on Wednesday, while Australia face Greece.
The ATP Cup is one of six events being held at Melbourne Park this week to allow players to prepare for the Australian Open, which begins on 8 February.