It is probable that the Colts have Bienemy in mind... or someone else on the coaching staff of the 2 teams.
Just as obvious is that they have not settled Morris. If they really wanted him as first choice, it would already be a done deal.
He has to know he's the back up plan if the Colts can't get the guy they really want from the Eagles or Chiefs.
I imagine it is more likely than not that he'll be back. But, the Rams being good guys are willing to wait to give him every chance, and an open door to return if it doesn't happen for him. This is one of the reasons coaches come to the Rams, knowing they'll enhance their resumes and get full team support should they be offered a promotion elsewhere.
