Evans wasn't good at being effective in the primary routes gailey requires. Lot of gailey's offense is quick slants and over the middle within 20 yards type throws.
However, I believe that when we go 4 or 5 wide spiller will be used as the replacement for evans as the streaker/burner to draw coverage away from the middle of the field. He did this well at clemson and I bet that is what the plan is.
I wouldn't worry too much about Evans being gone, all he did was draw double teams and run streaks we have Spiller who can do the same thing IMO