The Manchester City striker missed the last 16 win over Switzerland due to a thigh injury that saw him withdrawn in the first half of the final Group F game against Nigeria.
But Aguero, plagued by hamstring problems for much of last season, is on the road to recovery, his return to training leading many to believe he would feature on Saturday in Brasilia.
Sabella, though, has downplayed expectations, suggesting the 26-year-old may not even be ready for a place on the bench.
He said: "Aguero is getting better. We're going to see how he does to decide whether he'll be on the bench."
Despite reaching the quarter-finals of the competition, Argentina have come in for some criticism after failing to find their best form.
That was particularly evident against Switzerland, when Angel di Maria's strike at the end of extra-time ultimately earned a 1-0 win.
Sabella admits his side have had a reality check, saying: "Argentines often think they're better than they are. Sometimes that's a good thing, sometimes it's not."
While the weight of expectation is great, Sabella can at least enjoy the knowledge that bitter rivals and host nation Brazil are even further under the microscope.
Indeed, much hoopla has surrounded the revelation that Brazil coach Luiz Felipe Scolari has called in a psychologist to help his side - something Sabella does not believe is necessary for Argentina.
He added: "We handle things differently.
"The pressure on Brazil is greater. We try to relax."
