Bucharest - Sixth seed Viktor Troicki was knocked out of the Nastase Tiriac Trophy on Monday, losing to Spain's Daniel Gimeno-Traver on the first day of the tournament.
Gimeno-Traver, who was runner-up in the Grand Prix Hassan II earlier this month, beat Troicki 5-7, 6-3, 6-1 for his first win over the Serbian in four meetings.
Elsewhere, Malek Jaziri won three-quarters of his first service points to defeat Florian Mayer 4-6, 6-4, 7-5 in just over two hours.
Borna Coric and Mikhail Youzhny will meet later Monday.
Results on the first day of the Bucharest ATP tennis tournament (x denoted seeding):
Daniel Gimeno (ESP) bt Viktor Troicki (SRB x6) 5-7, 6-3, 6-1
Borna Coric (CRO) bt Sergiy Stakhovsky (UKR) 6-2, 6-7 (4/7), 7-6 (7/2)
Malek Jaziri (TUN) bt Florian Mayer (GER) 4-6, 6-4, 7-5