La Albiceleste advanced through Group F without dropping a single point, although all three victories were by single-goal margins.
"We know we have to be very focused and maintain balance," Sabella is quoted as saying by ITV Sport.
"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."
Tomorrow's game kicks off at 5pm in Sao Paulo, with the winner facing either Belgium or USA in the quarter-finals.