Australian wildcard Alexei Popyrin has fallen at the first hurdle at the inaugural Adelaide International ATP tournament.
The emerging 20-year-old has been beaten in three sets by Serbia's Laslo Djere in their first-round encounter.
Two seeded Americans - Taylor Fritz and Reilly Opelka - also exited on Sunday's opening day.
Djere, the world No.39, defeated Popyrin 7-6 (7-3) 3-6 6-4 in the first centre-court night fixture at Adelaide's redeveloped Memorial Drive.
"It was tight," Popyrin told AAP.
"He played well ... I performed pretty well; I just didn't come out on top."
The Serb held the only break point in the first set, which was in the opening game, but couldn't capitalise and the set went on serve until he took control of the tiebreak.
Djere won the initial two points and held command, losing just three points to claim the first set.
But world No.94 Popyrin, who reached the Australian Open third round last year as a wildcard, instantly hit back by breaking Djere's serve in the opening game of the second set.
Popyrin ploughed on, twice holding serve to love before breaking Djere again in the ninth game to secure the second set 6-3.
The third set was on a knife-edge at 3-3 and 30-all on Popyrin's serve when a momentum shift arrived: a point was replayed when the Australian stopped playing after hearing a linesman call out.
"I heard him call it out, and he actually did call it out and nobody else heard him," Popyrin said.
The Australian lost the next point, then double-faulted to give Djere a coveted break which proved decisive.
Earlier, American fifth seed Fritz was beaten by Kazakhstan's Alexander Bublik, 6-4 7-6 (7-4).
And Uruguay's Pablo Cuevas downed Fritz's compatriot, eighth seed Opelka, 5-7 7-6 (9-7) 7-6 (7-2).
Australian Associated Press