Australian qualifier Alex Bolt has lost in straight sets to world No.96 Argentine Carlos Berlocq at Winston-Salem Open in North Carolina.
The 24-year-old Bolt lost 6-2 6-4 in the first round of the US Open lead-up event on Monday.
Bolt, ranked 301 in the world, was the only Australian in the main draw of the ATP tournament after coming through two rounds of qualifying.
Briton Kyle Edmund advanced into the second round with a routine 6-2 6-3 win over Italian Thomas Fabbiano.
Fifth seed Pablo Cuevas was sent packing by Jan-Lennard Struff, who downed the Argentinian 7-6 7-5.
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Local hope Donald Young enjoyed a comfortable outing against Brazil's Rogerio Dutra Silva, winning 6-4 6-2 as compatriot Taylor Fritz downed Malek Jaziri of Tunisia 4-6 6-4 6-3.
Julien Benneteau triumphed in the battle of the Frenchmen, beating Pierre-Hugues Herbert 6-3 6-2 while Andrea Seppi beat Janko Tipsarevic 6-2 6-2.
Marton Fucsovics, Marcos Baghdatis, Andrey Rublev, Damir Dzumhur, Yen-Hsun Lu and Horacio Zeballos were also first-round winners.
