Chanot will start, I bet.
EDIT: Now that we have Chanot I wonder if we should play Mena Chanot Brillant as a back three and then put Bravo on with Iraola as a second DM. Would give us more passing options out of the back and in the center of the but might also stifle our attack too much. Might be worth trying while Mata is out, though.
Could also try RJ in some sort of weird roaming attacking position that switches between being a wing back and a DM along side Iraola. Like some sort of DM version of an inverted fullback if you can imagine that.