Istanbul - Top-seeded Australian Bernard Tomic was left waiting for his first European claycourt win of the season when he slumped to defeat to Argentina's Diego Schwartzman at the Istanbul Open on Thursday.
World number 23 Tomic lost his opener in Bucharest last week and struggled again in Turkey, losing 6-2, 6-2 to world number 87 Schwartzman in 64 minutes.
"I feel great here," admitted Schwartzman, who lost to eventual champion Roger Federer in last year's semi-finals.
"I'm playing well on these courts, which are slow. I tried to be focused today and I think I played a great match."
Schwartzman goes on to face Bosnia's Damir Dzumhur, who beat Illya Marchenko 6-3, 5-7, 6-3, for a place in the semi-finals.
Ivo Karlovic recorded the 300th match win of his career -- and first of an injury-hit 2016 -- when the 36-year-old beat Dusan Lajovic of Serbia 7-6 (13/11), 7-6 (9/7).
Karlovic snapped an eight-match losing streak during which he has struggled with a knee injury.
The giant Croatian, seeded at three, next faces either fifth-seeded Spaniard Marcel Granollers or South Korea's Hyeon Chung.