Fancied among the favourites before the tournament began, Argentina failed to hit top form in the group stages, although they still qualified in first place, winning their matches against Bosnia-Herzegovina, Iran and Nigeria.
Argentina's progression set up Tuesday's last 16 clash with Switzerland in Sao Paulo, and Sabella knows all too well that knockout football is unforgiving.
"We know we have to be very focused and maintain balance," he said on Monday.
"Obviously at this stage there is no margin for error, in the group stage there is chance of a recovery.
"We have to be very focused. Errors become more and more expensive."
Lionel Messi, Argentina's captain and talisman, showed glimpses of his supreme quality in the side's Group F campaign, with four goals in three matches.
"He is doing a great World Cup," added Sabella.
"It's what I expected of him, his colleagues, the public, and everyone.
"I am happy for the team and for him. He is a key player for us."
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