If I had to guess, we try to find a way to get Evans on the field 'with' Choice or Grant.
We'll put the 5 best ball carriers on the field each play and in some situations a tailback like Evans at flanker will make more sense than a 3rd or 4th guy in a reciever or TE spot.
We won't give up a great blocker who can run and catch like Cox most of the time, but a 2nd tailback spot or slot position for Evans and/or Grant would be likely (at times) if I had to guess. I'd expect Grant to play a lot in leiu of Choice, much like Choice did for PJ.
We'll find a way to get the 5 best ball threats on the field. Depending on the situation, it's gonna be Calvin, Choice, and for the next 3 - a host of other combinations with Cox a 'lot', JJ, Dunlap, big Demaryus Thomas, other WR's, 1 or 2 TE's at a time, and the now - very deep, tailback crew.
Heck - the way we run Calvin - he's off the field at times. When that happens, we need guys like Evans and/or Grant in there somewhere with Choice plus the best of the next 4 instead of 3. Grant has already proven he can play slot, so I'd expect him or Evans there at times.
To me, the faster, bigger version of Grant, and the explosive Evans both are almost too good not to each play a part of that mix, even if not just to keep fresh legs while Choice gets a breather.