I think it could be the 13th or the 15th for one player, probably Holliday. There won't be more than that this early unless there's an injury. Kjerstad certainly deserves a promotion, but we haven't seen Cowser get the ABs, add Kjerstad to the mix and it gets worse.
Hopefully, we see Cowser playing LF regularly and Hays and O'Hearn turning into essentially a platoon. Hopefully Cowser gets a few looks in CF, too, giving Mullins a break here or there.
The next most likely guy to move after Kemp, is probably Urias and that could be an opening for Mayo...but it's hard to find an opening for anyone else on this team until the team is ready to move on from O'Hearn--and I don't see that happening for a while.