British number three Kyle Edmund lost in straight sets to defending champion Guillermo Garcia-Lopez in the second round of the Nastase Tiriac Trophy.
The Spaniard, 32, won 6-3 6-3 in Bucharest to deny 21-year-old Edmund a first clay-court quarter-final.
Edmund, ranked 55 places lower at 92 in the world, saved nine of 12 break points but could not force one on the Garcia-Lopez serve.
The match had been postponed on Wednesday because of heavy rain.
Britain's Colin Fleming and Jonathan Erlich of Israel fought back to beat Argentina's Guido Pella and Czech Lukas Rosol 2-6 6-4 10-6 in the doubles.