I'll make the argument that he is.
I don't think anyone has been this bad for this long and kept his job.
Folks said that Ryan Howard would be a comp for a Davis deal gone bad...Howard at least still hit a bit during his decline.
I think that answer will depend on how many other guys you have that can go 5+ innings.
If I had to guess, you are lucky to have 3 guys in a rotation that give you 550 innings.
I think if you can get 3 guys to do that and then mix and match the other 2 days, you are in good shape. I could see that being the best way to maximize your staff. Most starters struggle once they go through the lineup 2-3 times. So, don’t ask them to do it.