PERTH: Stefanos Tsitsipas found his winning touch on his return to action from injury as he led Greece to a 3-0 win over Japan on Friday in group play at the ATP-WTA United Cup.

The former world number three dispatched Shintaro Mochizuki 6-3, 6-4 in singles as he played his first match in almost four months after a recurring back injury forced him to take a break from the sport.

“I’ve had a lot of uncertainty, I didn’t know if I could compete,” Tsitsipas said.

“But to play at this level is something I’m very grateful for.

“I’m healthy and that’s the most important thing in the world.

“I hope this tournament can give me some confidence before the Australian Open [Jan 18-Feb 1],” added the 27-year-old two-time Grand Slam finalist.

Team-mate Maria Sakkari began the tie with a 6-4, 6-2 defeat of Naomi Osaka.

Japan’s former world number one is suffering with a head cold and played far from her best in Perth.

“I was not operating at the percent I would want, I did not play amazing,” the four-time Grand Slam champion said.

“Honestly, it was not a bad first match for what it was.

“I’m thankful I have another to play. I need to not be afraid of making mistakes.”

Tsitsipas and Sakkari then teamed up for Greece’s dead-rubber mixed doubles tie to beat Japanese duo Yasutaka Uchiyama and Nao Hibino 6-2, 6-3.

Earlier, Sebastian Baez and Solana Sierra led Argentina to a 3-0 defeat of Spain.

World number 45 Baez got Argentina on the scoreboard with a 6-4, 6-4 victory over Jaume Munar, earning a surprise win on hard court after just three victories in nine matches on the surface last season.

The South Americans clinched the win when 66th-ranked tournament debutante Sierra held her nerve for a 6-4, 5-7, 6-0 defeat of Jessica Bouzas Maneiro.

The 21-year-old, who reached the fourth round at Wimbledon last year, said: “I knew I had to be tough.

“I’m super-happy with my level.”

Argentina then won the mixed doubles rubber in straight sets.

Ties at the United Cup comprise one men’s and one women’s singles and a mixed doubles, with group winners in each host city — Perth and Sydney — advancing to the quarter-finals along with the best runners-up.

Published in Dawn, January 3rd, 2026