21-year-old Russian Anastasia Potapova beat world number two Anett Kontaveit in the quarter-finals of a tournament in Prague.
For Potapova, it is her second win in nine matches against top-10 tennis players. She won her first at Roland Garros 2009 against No. 5 Angelique Kerber.
Potapova reached the semi-finals at her third consecutive WTA tournament. It is the eighth time in total that she has reached the top four at the main tour level.