By Jeremy Harness

Wednesday was not considered a great day for the Americans in the Bank of the West Classic draw. Thursday, on the other hand, turned out just a bit better.

American Varvara Lepchenko fired the loudest shot of the entire tournament thus far in the second round of this tournament, being held at Stanford, as she pulled off the upset over top-seeded Caroline Wozniacki in straight sets, 6-4 and 6-2, on Thursday.

Lepchenko seized the advantage early and held onto it throughout the match by maintaining the edge in first serves, as she converted 26 of 33 (78 percent) overall. She also blasted three of her serves past Wozniacki for aces.

She added to the advantage by breaking Wozniacki’s serve four times and then took advantage of the WTA’s fifth-ranked player’s three double faults in the second set.

This was Lepchenko’s first-ever win over Wozniacki, who had won the previous four head-to-head matches, including last year in Miami that saw Wozniacki prevailing in a 6-0 and 6-1 blowout.

Lepchenko will face Mona Barthel, who herself pulled off an upset in the second round Wednesday night, shocking fellow German Andrea Petkovic in three sets, 5-7, 6-2 and 7-6.

After dropping the first set, Barthel quickly claimed the edge in the second set against the 17th-ranked WTA singles player by winning 75 percent of her first serves and was not broken a single time. Meanwhile, Barthel broke both of Petkovic’s serves in that set.

In the other matches Thursday, Angelique Kerber, the WTA’s 14th-ranked singles player, was a straight-sets winner over Ana Konjuh. The German was dominant in every category, including efficiency (Kerber had only one double fault while Konjuh committed four of them).

Kerber will face Agnieszka Radwanska, who rallied to beat Japan’s Misaki Doi, 1-6, 6-2 and 6-0, on Thursday, while Karolina Pliskova was a winner in straight sets, 7-5 and 6-2, over Kimiko Date-Krumm.