Struggling former world number two Alexander Zverev crashed to a second straight defeat of the season Monday at the United Cup, dismissed by American Taylor Fritz in just 64 minutes.
The German two-time ATP Finals champion slumped 6-1, 6-4 to the world number nine in Sydney as he continued his return from serious injury.
It followed a straight-sets loss to 81st-ranked Czech Jiri Lehecka on Saturday in his first competitive match since tearing three right ankle ligaments during his French Open semi-final against Rafael Nadal in June.
"I've just been practising, kind of dialling in some of the things that didn't feel great for me in the first match," said Fritz, referring to his opening United Cup win, also against Lehecka. "I'm still working, practising and trying to improve.
"I love playing team competition, I've always performed in team events," he added. "It brings a different energy."
Fritz had a breakthrough year in 2022, beating Rafael Nadal in the final at Indian Wells to go with titles in Tokyo and Eastbourne.
The mixed team tournament features 18 countries playing in Sydney, Brisbane and Perth.
The winners of the two groups in each city advance to a City Final on Wednesday, with whoever comes through that making the final four.