Kudermetova and Kasatkina lead Russian charge in St Petersburg Open

Number two seed Kudermetova edged past Kamilla Rakhimova 7-5, 3-6, 7-6 (5), while eighth seed Kasatkina also needed three sets to see off Aliaksandra Sasnovich 5-7, 6-3, 7-6 (2).

Wildcard Margarita Gasparyan held off Katerina Siniakova 6-4, 6-4 and qualifier Anastasia Gasanova shocked fifth seed Anastasia Pavlyuchenkova 1-6, 7-6 (8), 7-6 (4).

They joined fellow Russians Vera Zvonareva, Ekaterina Alexandrova and Svetlana Kuznetsova in the last eight, with Romanian qualifier Jaqueline Cristian also in the line-up.

The previous highest number of Russians in a WTA quarter-final line-up was six, set at Moscow 2005 when Kuznetsova was joined by Dinara Safina, Elena Dementieva, Maria Sharapova, Anastasia Myskina and Elena Likhovtseva.

The last time a single nation had as many players at this stage of a WTA event was in Oakland in 1993 when the United States produced seven of the eight quarter-finalists.