Alex Bogdanovic saw his hopes of breaking new ground by making round two of the US Open ended by Alex Calatrava.
The Spaniard beat the British number four, who was playing in the main draw of a Grand Slam outside Wimbledon for the first time, 6-3 3-6 4-6 6-1 6-4.
Bogdanovic recovered after a slow start and repeatedly served his way out of trouble as he went two sets to one up.
But the 20-year-old could not keep up the pace as Calatrava held on, despite a nervous end to the fifth set.
Calatrava goes on to face experienced Czech Jiri Novak in the second round.
Bogdanovic won three matches in qualifying without losing a set and should still see his ranking rise from 206 despite the defeat.