I think you play the regulars. If guys are hurt maybe you don't push it and play them like you would if you are in the playoff mix.
I know JMV has suggested playing Chad Kelly but I probably wouldn't. I see him as the back-up at best over Brian Hoyer going forward. Maybe you want to play him to evaluate that possibility but the Colts likely have a good idea on this already.
Whether it's Jacoby or Chad Kelly I don't think either one will change how the Colts move forward at the quarterback position.
I believe Jacoby is due a signing bonus before free agency begins that will essentially lock him onto the roster for 2020. I expect the Colts to pick that up. Jacoby will be the starter again in 2020. The Colts will try and improve the receiver group and hope to be healthier next year.
They probably want to upgrade that position if the right player is available in the draft and if he is they take him and he is the backup next year to Jacoby.
There really isn't a lot of young guys not playing already. With so many injuries, especially on offense, they have to play who is healthy and don't have much of a choice who to play in some cases.