I don't think there are Perry Vs. Mills guys. Perry is the GM and Mills is the Pres.
Guys that play best play. Trey gets a chance because he is playing well. No doubt there was a deal made: "come, rehab, get it together for half a season and then we'll give you a chance". "If you do that, you will get the call to show what you got".
If not, buh bye. No drama, no "My guy vs his guy".