United Cup, Day 1 Preview: Naomi Osaka begins promising 2026, Stefanos Tsitsipas back from injury

Traditionally, the tennis tours can’t wait—and don’t wait—to get the new year underway. For the past decade or so, they’ve been jumping the gun and starting their seasons on December 31st. So it comes as a little bit of a (pleasant) surprise to see that the sport is easing us in, relatively speaking, to 2026.

We begin with a day of rest and recovery on January 1st, before the United Cup kicks off in Australia on the 2nd. Even then, it’s not quite full speed ahead: Only two team matches are scheduled, both in Perth. From then on, it’s four per day.

Here’s a look at what’s in store for us as the curtain rises on tennis in 2026.

📲🖥️ Stream the 2026 United Cup on the Tennis Channel App!

Who’s playing who?

Day Session: Spain vs. Argentina, from Group A, will begin bright and early, at 10 A.M. local time in Perth (9 P.M. ET)

Evening Session: Greece vs. Japan, from Group E, will start not before 5 P.M. local time (4:00 A.M. ET)

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Spain vs. Argentina: What to Watch

Jaume Munar vs. Sebastian Baez

At 28, with his countryman Carlos Alcaraz now reigning supreme, Munar no longer has to shoulder the (impossible) burden of being his nation’s Next Rafa. That seemed to suit Munar in 2025. He had his best season and finished a career-high No. 33. He has also made himself easier to watch by losing the extraneously loud grunts that once accompanied every swing of his racquet. Is it too late for him to be the Next David Ferrer? Munar will start against another grinder, the 45th-ranked Baez, in what should be a tenacious and competitive opening bout to the year.

Jessica Bouzas-Maneiro vs. Solana Sierra

Neither of these women are household names, and may never be. But they’re likely to pop up on our radar more in the coming months and years. They’re young: Bouzas-Maneiro is 23, Sierra is 21. They’re improving: Each reached a career-high ranking—No. 40 for the Spaniard; No. 64 for the Argentine—in 2025. And both have ball-striking talent that should take them higher in 2026.

Greece vs. Japan: What to Watch

Naomi Osaka vs. Maria Sakkari

At the start of the decade, Osaka and Sakkari looked like the future of the WTA. Osaka won four majors and reached No. 1. Sakkari made it deep at several Slams and as high as No. 3. Now they’re veterans—Osaka is 28, Sakkari is 30—who can’t get off the comeback trail.

Osaka went much farther on that trail in 2025. She reached the US Open semifinals, finished 16th in the rankings, and started what appears to be a productive new partnership with Iga Swiatek’s old coach, Tomasz Wiktorowski. Osaka also started fast last January when she made the final in Auckland, and she has won the Australian Open twice. There’s no better time or place for her to take the next step up.

Stefanos Tsitsipas vs. Shintaro Mochizuki

“I couldn’t ask for anything better,” Tsitsipas says of his season opener, which will take place in Greek-centric Perth. More important, Tsitsipas says he’s healthy again after a back injury cut his 2025 short.

Can the 27-year-old take some inspiration from Osaka? Like her, he has thrived Down Under in the past, having made the Australian Open final once, and the semis three other times. Like her, his game and confidence took an extended dip, and his ranking—now No. 36—isn’t what it used to be. And like her, it still feels too late to write him off. He’ll start the new season with his first match against Mochizuki, a 22-year-old who is too talented to be 99th in the world for much longer.

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Who’s going to win?

Spain d. Argentina 2-0

Greece d. Japan 2-1