Edmund lost in the second round at Wimbledon last month
British number Kyle Edmund was knocked out of the Washington Open in a three-set quarter-final defeat by Germany's Peter Gojowczyk.
World number 122 Gojowczyk, who defeated 2014 champion Milos Raonic in the last round, won 6-3 4-6 6-3 in one hour 58 minutes.
He will play Marin Cilic or Daniil Medvedev in his first 500-level semi-final on Saturday.
Edmund, 24, hit 37 unforced errors and four double faults.
Gojowczyk lost in Washington qualifying but made the main draw as a lucky loser after Bernard Tomic's withdrawal.
He beat Andrey Rublev, Alex de Minaur in addition to Raonic and Edmund on his way to the semi-finals.
The 30-year-old broke world number 34 Edmund's serve early in the opening set before the Briton scuppered his own break point in the sixth game.
He lost the set when he was broken once again by a clean Gojowczyk winner, but rallied in the second, going a break up midway through before serving out the set to restore parity.
But Gojowczyk dominated the decider as Edmund dropped his serve early on, though the German needed five break points to seal his place in the next round.