Angelique Kerber is through to the semi-finals of the Bank of the West Classic following her comeback win over Agnieszka Radwanska on Friday.

The quarter-finals at the Bank of the West Classic in Stanford.

The tournament has seen plenty of upsets so far and Angelique Kerber wasn't about to disrupt the status quo.

The German took on second-seed Agnieszka Radwanska.

Despite dropping the first set, the fifth seed came back to secure the second and third to set-up a semi-final clash with Elina Svitolina.

The number eight seed also came back after dropping the first set in her quarter final match against Alison Riske.

The wildcard was serving for the match at 5-4 in the second set when Svitolina rallied.

The Ukrainian then dominated the third set, where she lost only one game to progress.

American player Varvara Lepchenko was made to work for her place in the last four.

She defeated Germany's Mona Barthel, who took the first set in a tie-break.

Lepchenko, who knocked-out top-seed Caroline Wozniacki in the previous round, rallied from there though, taking the second and third sets in straightforward fashion.

Her semi-final opponent will be Karolina Pliskova who progressed with a straight sets win over Ajla Tomljanovic.