Washington (AFP) - Georgia's Nikoloz Basilashvili upset Croatian top seed Ivo Karlovic 7-6 (7-2), 6-3, Thursday to reach the quarter-finals of the ATP Memphis Open.

A week shy of his 25th birthday, the world No. 67 won all 37 of his first serve points and took only 69min to dispatch hard-serving 37-year-old Karlovic, ranked 20th in the world.

Basilashvili, seeking his first ATP crown, advanced to the last-eight at the indoor hard court event, where he will meet Australian qualifier Matthew Ebden, who downed US teen Taylor Fritz 6-4, 4-6, 6-3 after 1hr and 42 min.

Kazakhstan's Mikhail Kukushkin dispatched Barbados qualifier Darian King 6-3, 6-0 in 70min to book a quarter-final spot against US fourth seed Steve Johnson, who rallied to oust compatriot Tim Smyczek 3-6, 6-4, 6-2.

Kukushkin connected on 65 per cent of his first serves and won 82 per cent of his first serve points while King managed to take only 36 per cent of his first serve points.

Friday's other quarter-finals will pit US second seed John Isner against compatriot Donald Young and American Ryan Harrison against Bosnian Damir Dzumhur.