CHICAGO, IL, USA - Russia's Anna Blinkova scored the upset of the day in the Oracle Challenger Chicago when she beat top seed Danielle Collins 7-6, 6-2 to set up a quarterfinal clash with Sachia Vickery.

Vickery beat another American, wildcard Allie Kiick, 6-4, 6-0 to grab her own spot in the next round; while another home favorite Madison Brengle fell to Tatjana Maria, 6-3, 6-2.

The German now faces Canada's Francoise Abanda, who beat Johanna Larsson of Sweden 3-6, 6-3, 6-3.

Second seed Petra Martic is still in the draw; the Croatian got past Sesit Karatantcheva of Bulgaria 6-4, 6-2.

In a hard-fought duel, Mona Barthel beat Zarina Diyas in three sets, 6-2, 3-6, 6-3, to secure a quarterfinal clash with Dayana Yastremska, who beat US qualifier Kristie Ahn 7-6(3), 6-4.

The longest match of the day - at an grueling three hours and 14 minutes - was wildcard Varvara Lepchenko's win over Sara Sorribes Tormo, 6-4, 6-7, 6-4.

FRIDAY'S ORDER OF PLAY

COURT 1
Starting at 10am

[Q] Francoise ABANDA (CAN) v Tatjana MARIA (GER) [4]

After 1 ATP match

[WC] Varvara LEPCHENKO (USA) v Petra MARTIC (CRO) [2]

COURT 2
Starting at 10am

After 1 ATP match

Anna BLINKOVA (RUS) v Sachia VICKERY (USA) [6]

After 1 ATP match

Mona BARTHEL (GER) / Kristyna PLISKOVA (CZE) v Darija JURAK (CRO) / Xenia KNOLL (SUI) [2]

COURT 3
Starting at 11am

Mona BARTHEL (GER) v Dayana YASTREMSKA (UKR)

After 1 ATP match

Asia MUHAMMAD (USA) / Maria SANCHEZ (USA) v Evgeniya RODINA (RUS) / Dayana YASTREMSKA (UKR)