Argentina - without talisman Lionel Messi due to injury - had beaten Italy 2-0 in Manchester on Friday but found Spain far too strong on Tuesday.
And Sampaoli conceded there is a lot of work to do to ensure Argentina do not suffer similar embarrassment at the World Cup in Russia.
"We have to take charge of this game, these things cannot happen to us at the World Cup," Sampaoli said.
"Spain have slapped us, we have to keep working.
"They are atypical results that can change the coach's perspective if everything is not analysed.
"I'll have to break the match down well and decide... You have to solve the emotional issue.
"We did not expect so much force from the opponent."
Argentina kept Spain under control in the first half and went into the break at 2-1 down.
But Sampaoli's side fell apart after the interval with Isco in inspirational form, the Real Madrid playmaker scoring his first international hat-trick.
"In the second half, Spain grabbed us by attacking very directly," Sampaoli added. "Very quick goals came and that made the difference in the result.
"The result makes it clear that we need to take this game to assemble the final squad and keep working so that things do not happen [like this] in the World Cup.
"The goal was to defend ourselves more with the ball, we did not have defensive aspects to achieve balance and the solidity that we expected."