French Open wildcard Chris O'Connell has been defeated in the first round of the ATP Tour event in Serbia.
World No.128 O'Connell, who only last week was guaranteed his maiden appearance in the main draw of the Paris major, lost 3-6 7-6 (9-7) 7-5 to fellow qualifier Andrej Martin at the Belgrade Open.
The 26-year-old Sydneysider will now turn his focus to the year's second grand slam, with opening round action commencing on Sunday.
"Being able to compete in my first Roland Garros main draw is a dream of mine," O'Connell said after his wildcard spot at the French Open was granted.
Meanwhile, Pablo Cuevas carried momentum from his semi-final run at the Geneva Open to upset seventh-seeded local Miomir Kecmanovic 6-3 6-2.
Dusan Lajovic reached the last 16 in the Serbian capital with a comfortable 6-3 6-3 win over Ricardas Berankis.
Eighth-seeded Federico Delbonis accounted for Lukas Klein 3-6 6-4 6-2.
Spain's Fernando Verdasco, a former Australian Open semi-finalist, beat France's Lucas Pouille 7-5 6-2.
Top seed and world No.1 Novak Djokovic will commence his campaign on home soil against Mats Moraing, who outlasted Egor Gerasimov 4-6 7-6 (9-7) 7-5.