The 29-year-old suffered a broken rib in a car crash during the international break, with initial estimates putting his recovery time at up to six weeks.
The Argentine has made a speedier return than expected, however, and participated in a full training session on Friday, subsequently tweeting that he is "ready".
"He has had his first training session and he did quite well," Guardiola told reporters at his pre-match press conference this afternoon. "Maybe he could be back for tomorrow.
"He's not 100%. He explained what would happen, what would have happened, now we are happy he is back to training."
Aguero has scored six goals in six league games for City so far this season to help them to the top of the table.