By Jeremy Harness

STANFORD – And then there was one.

Varvara Lepchenko, fresh off of her upset of top-seeded Caroline Wozniacki the previous evening, kept rolling along Friday night in a 6-7, 6-2 and 6-3 runaway win over Mona Barthel in their quarterfinal match to stand as the only American remaining in this Bank of the West Classic.

This marks the second straight semifinal appearance in this tournament for Lepchenko, who was born in Croatia but moved to the U.S. when she was 15 and got her American citizenship 10 years later.

“I’ve done very well here before, so I felt confident coming in here,” Lepchenko said. “I love playing in California.

“I definitely feel the appreciation from the fans playing in tournaments in the United States.”

While Barthel was very inconsistent with her serve – the German had six aces but counteracted that with six double faults – Lepchenko focused on keeping the ball in play and relying on her ground game to get ahead in the match and stay there.

Lepchenko went to the net more often and put the pressure on Barthel, who showed her wear by committing 31 unforced errors on Friday to Lepchenko’s 19.

“My focus was not there (in the first set),” she said. “I tried to loosen up in the second set, and I think it worked out for me.”

She battled with pneumonia earlier in the year and said that she starting feeling like she was in better playing shape during the AEGON Eastbourne International, the week before Wimbledon, which was held in late June. She said that after Wimbledon, she began working primarily on improving her fitness, and she attributed that to her continued success this week.

” I worked very hard to get ready for the hard-court season, and it’s starting to pay off now,” she said. “It gives you confidence that you can find your way throughout the match. I realized that, hey, I’ve got that base now, so I should be able to do this.”

She will face Karolina Pliskova, who downed Ajla Tomljanovic in straight sets, 6-2 and 6-4, earlier in the afternoon, Saturday at 12pm PST.

Pliskova was dominant in every phase of the game, particularly in the first-serve category. She won 82 percent of her first-serve points – while Tomljanovic won only 58 percent – while also saving all six of her break points.

Besides Lepchenko, the other American in the quarterfinal round was Alison Riske, but she would join Lepchenko into the semis. She took the first set of her quarterfinal match against Ukrainian Elina Svitolina but dropped a hard-fought second set, 7-5, to extend the match.

From there, Svitolina shut the lights out on Riske by a 6-1 count, using three aces in the set as well as an edge in first-serve points to her advantage.

Svitolina now has a Saturday date (4pm PST, to be exact) with Angelique Kerber, who won an absolute thriller in Friday’s nightcap over Poland’s Agnieszka Radwanska, 4-6, 6-4 and 6-4, in a match that lasted almost two-and-a-half hours.

Kerber dropped the first set and was down in both the second and third sets before rallying to win both of them, getting huge points when she needed them and responding to Radwanska’s clever ground game with some crafty shots of her own.

In the final set, Kerber trailed 4-3 but held serve to tie things up, and with the game tied at 30-30, Radwanska double-faulted to give Kerber the advantage. Kerber won the ensuing point to get a crucial serve break and take the 5-4 lead before holding serve to close out Radwanska and move on.

Kerber came away victorious despite the fact that she was beaten in two crucial statistical categories: Radwanska won 11 more points at the net while committing 32 unforced errors to Radwanska’s 28.