Gavrilova exits at San Antonio Open

Australian Gavrilova, the top seed at the WTA 125K series event, went down to Riske 6-4 6-4 in one hour, 32 minutes on Thursday.

Riske broke five times as Gavrilova struggled on serve, the Russia-born right-hander serving at just 58 per cent with six double faults.

With her win, Riske set up a clash against Anna-Lena Friedsam in the semi-finals after the German battled past Ana Konjuh 6-4 4-6 6-2.

Bulgarian Tsvetana Pironkova cruised into the last four, thrashing Konjuh's Croatian countrywoman Donna Vekic 6-2 6-1.

The only seed left in the draw is Misaki Doi, who was a 6-3 6-3 winner against Samantha Crawford.