Rookie QB's seem to love using tight ends as a regular target so i would stick with chandler, plus jacksonville has done surprisingly well against the pass this year. That has to do with the fact that they always seem to be losing so their opponents just run the ball, which is something to take into consideration. If Indy gets out ahead early it'll be Trent Richardson for the rest of the game, not much passing.
I would say put gates in. Davis is coming off an injury and that always makes predicting how he'll perform tough, especially since he's still listed as questionable for this week. i think gates is the more reliable option since he's had 2 solid games in a row now.