United Cup, Day 7 Preview: Can Belgium pull off another upset vs. the Czechs?

Christian Harrison is the least-heralded of the U.S. United Cup team’s starting players. But it was the well-traveled, oft-injured—he’s had “at least” eight surgeries—31-year-old who carried the team across the finish line in its quarterfinal against Greece on Wednesday in Perth.

The match was tied at 1-1. The deciding doubles, between Harrison and Gauff and Stefanos Tsitsipas and Maria Sakkari, was tied at one-set all. The U.S. sprinted to a 5-0 lead in the super-tiebreaker, only to see Greece close the gap to 9-8. That’s when Harrison took over: He served, stuck a forehand volley, and put his last volley between Tsitsipas’s legs to send the States into the semifinals for the third time in four years.

Elsewhere, Switzerland also advanced to the semis, with a 2-1 win over Argentina, and Poland reached the quarters for the fourth straight year with a 3-0 win over the Netherlands.

That sets up some intriguing knockout-stage matches for the near-future. On Friday, Poland will take on Australia, in a battle between two very vocal fanbases. The winner will play the defending champion U.S. in the semis over the weekend.

Before that storm, though, we’ll get a relatively quiet Thursday. Just one quarterfinal is on the schedule, in Sydney, between Belgium and Czechia. The winner plays Switzerland.

Who’s playing who?

Sydney

Belgium vs. Czechia quarterfinal (5:30 P.M. local; 1:30 A.M. ET)

Who to watch

Jakub Mensik vs. Zizou Bergs

🖥️📱 Click here for live coverage on TennisChannel.com (approximate start time 1:30 a.m. ET)

The 42nd-ranked Belgian and the 18th-ranked Czech have never played. Each is 1-1 in United Cup this week, and each seems like a guy who could reach greater heights in 2026 than he has before. Mensik will be the favorite: He’s ranked 24 spots higher, he’s four inches taller, he has a much more lethal serve. But based on his play in Davis Cup last fall and in United Cup so far this week, Bergs is a tough out when he’s competing for his country.

Barbora Krejcikova vs. Elise Mertens

🖥️📱 Click here for live coverage on TennisChannel.com (approximate start time 3:00 a.m. ET)

Is it really possible that these two 30-year-olds, who have played the same tour and gone deep at the same tournaments for more than a decade, have never faced each other? That’s what the WTA’s records say. Krejcikova is currently ranked 62nd, but has been as high as No. 2. Mertens is No. 19 right now, and has been as high as 12. The Czech is the artist with the wide palette of shots; the Belgian is the more straightforward, never-say-die fighter. Let’s see what they create together.

Who’s going to win?

Czechia 2-1