Bernard Tomic has been upset by world No.140 Darian King in the first round of the Memphis Open.
The Australian world No.32 lost 6-4 6-4 to Barbadian King.
The match was Tomic's first since his loss at the Australian Open last month.
The historic win was King's first in the main draw of an ATP World Tour event and his first over a top 50 opponent.
Australian Matthew Ebden fought back from dropping the first set to roll fellow qualifier Peter Polansky of Canada 6-7 (4-7) 6-3 6-1.
The world No.490 brushed aside the disappointment of dropping the opener in a tiebreak to reach the second round.
Australia's Jordan Thompson will play Nikoloz Basilashvili of Georgia in his opening round for the right to face top seed Ivo Karlovic.
Meanwhile, Ryan Harrison beat Konstantin Kravchuk of Russia 6-3 7-5 to set up an all American clash with No.3 seed Sam Querrey.