It’s the undercard, of course, the junior varsity version of the Family Circle Cup semifinals.

If today’s Serena vs. Sam showdown is the first-name only semifinal, it’s tempting to call Polona Hercog vs. Lucie Safarova the no-name semi. That would not be fair, of course, to two of the WTA Tour’s promising young stars, ranked 38th and 26th in the world, respectively.

“One of us is going to sneak through to the finals,” Hercog said after her 6-1, 6-2 dismissal of 2006 Family Circle Cup champion Nadia Petrova on Friday night on Daniel Island’s Stadium Court.

For either player, a berth in the Family Circle Cup finals against either Serena Williams or Samantha Stosur on Sunday would be a career breakthrough. Hercog, 21 and seeded 14th, has just one WTA title to her credit; Safarova, 25 and seeded ninth, has won four times.

Serena and Sam? They’ve combined to win 42 times (39 by Serena), and Stosur is the reigning U.S. Open champion. Hercog realizes that either she or Safarova will be heavy underdogs on Sunday. But she’s not ready to crown Serena or Sam as the champ.

“It’s a very tough tournament,” said Hercog, a Slovenian whose only WTA win came on clay last year in Bastad, Sweden. “I’m very happy with what I did so far, but the tournament is not over, and I’ll do my best to try to win every match that’s ahead of me.”

That starts today against the Czech Safarova, whose aggressive style was too much for fourth-seeded Vera Zvonareva in a 6-3, 6-3 win. Hercog and Safarova have split two previous matches; Hercog beat Safarova on clay at the French Open in 2010, while Safarova won their last meeting 6-3, 4-6, 6-3 last year on hard courts in Toronto.

“She’s fit and she’s hitting really hard, and she’s a very nice girl, too,” Hercog said of Safarova. “You just have to go into the match, you have to believe. I’ll try to mix up my game and let the best player win.”

This season, Safarova has been more on form; she beat a fourth-ranked Caroline Wozniacki in February and was 8-8 in singles play heading into the FCC. Hercog’s best win this year was her three-set upset of No. 7 Marion Bartoli on Thursday, and she was 5-12 coming in.

“I wasn’t giving up,” said Hercog, who had been 0-4 against Bartoli. “I kept believing.”