Keothavong struggled against the 34-year-old Craybas
British number one Anne Keothavong lost 6-3 6-2 to American veteran Jill Craybas in the first round of the East West Bank Classic in Los Angeles.
Keothavong, 24, up to a career-best 76th in the world rankings, was broken in the second game and never recovered.
But compatriot Katie O'Brien, ranked 150th, had one of the best wins of her career in the first round of the Slovenia Open.
The 22-year-old beat world number 44 Tsvetana Pironkova 7-6 (8-6) 4-6 6-2.
O'Brien was a break up in the first set before taking it on the tie-break and then squandered a 4-1 lead in the second to allow the Bulgarian fifth seed to level.
But the Briton regained her advantage at the start of the third and secured victory in some style.
"After leading 4-1 in the second set I lost five games in a row and I thought I had blown my chance, so I was really pleased I managed to regroup and the win in the third," said O'Brien.
O'Brien, who was close to breaking into the top 100 before Wimbledon, will face Russia's Vera Dushevina in the second round in Portoroz.