The Czech Republic and United States are the two most successful countries in Fed Cup history.
The U.S. won seven straight championships, from 1976-82, and the Czechs are three-time defending champions and have won a stout five of six.
The two collide April 22-23 in the Fed Cup BNP Paribas semifinals, but both teams will be seriously depleted of their usual stars.
Serena and Venus Williams, as well as Madison Keys -- all ranked within the WTA's top 12 -- will be missing for America, while No. 3 Karolina Pliskova, two-time major champion Petra Kvitova, Barbora Strycova and Lucie Safarova sit out for the Czech Republic.
Belarus and Switzerland face off in the other semifinal. The winners advance to the Nov. 11-12 final.
At the same time, these top-10 players are scheduled to compete in the World Group playoffs: No. 1-ranked Angelique Kerber (Germany), Simona Halep (Romania), Johanna Konta (Great Britain) and Elina Svitolina (Ukraine).
Here's what we'll be watching for:
USA vs. Czech Republic, Saddlebrook Resort, Florida, outdoor clay
Storylines: The key to this one could be whether Vandeweghe is feeling it -- or not.
She loves the big stage, as we discovered at the Australian Open. Vandeweghe, a 25-year-old Californian, beat No. 1-ranked Kerber in the fourth round and defending French Open champion Garbine Muguruza in the quarters before losing to Venus Williams in a three-set semifinal. Vandeweghe, who lost her only matches at Indian Wells and Miami, is also wildly inconsistent.
Davis is ranked No. 36 among WTA players and has put together a sterling 16-6 record so far in 2017. Rogers, who made the quarters last year at Roland Garros, likes to play on the dirt. Mattek-Sands is the No. 1-ranked doubles player in the world.
The Czechs have a Pliskova in the lineup, but it's 58th-ranked Kristyna, the twin sister of the more accomplished Karolina. Still, it was Kristyna who advanced to the quarterfinals last week in Switzerland -- where she lost to the 17-year-old and eventual champion Vondrousova, then-ranked No. 233, who had qualified her way into the main draw.
Siniakova is actually ranked 20 spots higher than Kristyna , although Siniakova lost her first match in Charleston to Monica Puig. Previously, Siniakova and Allertova have only played Fed Cup doubles, while Pliskova and Vondrousova are new to the format.
Of note: The United States seeks its first trip to the semifinals since 2010. Mattek-Sands is the only holdover from that team that lost in the finals to Italy. The choice of the slower clay makes sense with the absence of the three big hitters.
Belarus versus Switzerland, Chizhovka Arena, Minsk, Belarus, indoor hard
Storylines: On paper, this looks like a blowout. With Victoria Azarenka at home with her new son, Leo, the highest-ranked singles player for Belarus is ... No. 108 Sasnovich. But Sasnovich got to the semifinals of last week's tournament in Switzerland before losing to Anett Kontaveit.
It should be noted, this same Belarus squad hammered the Netherlands 4-1 in the previous round.
Switzerland has more firepower: No. 22 Bacsinszky, No. 54 Golubic and No. 131 Bencic. Only a year ago, Bencic -- who turned 20 last month -- was ranked No. 7 in the world.
Of note: Don't discount Hingis, who is ranked No. 8 in doubles. She's hoping to lift Switzerland into its second final ever. The first came in 1998 when Hingis, a teenager, was the WTA's top-ranked player.