Samoa captain Semo Sititi described his side's display as "inexcusable" after they were crushed 60-10 by South Africa.
Sititi was disappointed by Samoa's exit
The Pacific Islanders had been hotly tipped to push the Springboks for the runners-up spot in Pool C but rarely looked likely to trouble their rivals.
Sititi said: "There's no excuse about it. I think the attitude wasn't there.
"I think we ran out of petrol. All credit to the Springboks."
The Samoans conceded a total of eight tries as only Opeta Palepoi crossed the line for Samoa.
The result left Sititi's side third in the pool and out of the World Cup.
"It's a bit disappointing," said the Samoan skipper of his side's tournament exit.