Bernard Tomic is set to slip to his lowest ATP ranking since 2010 after bowing out of the Istanbul Open against sixth seed Viktor Troicki.
Tomic took the first set 6-3 but fell apart in the second, losing 6-0 before fighting back in the third but ultimately falling short 7-5.
Serb Troicki, who made the Istanbul semi-finals last year, hit 13 aces and broke the Australian five times to prevail in just under one hour and 50 minutes.
Defending points after reaching the quarter-finals last year, Tomic - who lost to top seed Milos Raonic in the last eight - is set to fall to No.233 in the world, his lowest ranking since June 2010, when he was ranked No.246.
Elsewhere on Monday, fifth seed Paolo Lorenzi advanced in straight sets while Troicki's countryman Laslo Dere won a tight encounter against Denis Istomin.
Argentina's Marco Trungelliti fought back from a set down to beat Ukraine's Elias Ymer.
