The Argentina international is yet to make his first-team debut for the Catalan giants, having picked up a serious calf injury towards the start of August.
Aguero has stepped up his recovery in training, though, and also featured for 25 minutes in a behind-closed-doors friendly last week.
Koeman has revealed that the former Manchester City forward will be in the squad against Valencia but has not indicated whether he could be in the starting XI.
"[Aguero] has improved a lot lately. He did 25 minutes the other day in the friendly match that we played. He is doing well, but he lacks physicality and match rhythm, and that is achieved by [playing] matches," Koeman told reporters.
"He will be on the list. His talent is known. He can give a lot. The best thing is that he is well, and by getting minutes he will be even better, as has happened with Ansu Fati."
The 33-year-old has a record of 74 goals in 175 La Liga appearances from his time at Atletico Madrid. body check tags ::