Grigor Dimitrov booked his place in the last eight of the Istanbul Open on Wednesday with a three-set win over Romania's Adrian Ungur.
The Bulgarian second seed failed to build on his advantage after winning a tight opener, but held his nerve in the decider to clinch a 7-5 4-6 7-5 win.
In the quarter-finals Dimitrov will meet fifth seed Jiri Vesely, who came from behind to beat Spain's Roberto Carballes Baena 6-7 (5/7) 6-2 6-2.
Fourth seed Federico Delbonis also needed three sets to overcome Dudi Sela 6-3 2-6 6-4, and eighth seed Albert Ramos-Vinolas finished strongly to beat Russia's Karen Khachanov 4-6 6-1 6-0.
In a first round match, Ukraine's Illya Marchenko beat Maximo Gonzalez of Argentina 6-3 3-6 6-1.
Source: PA
