It could be that Mirallas is injured, the club doesn't always tell us all the players that are injured especially if they are seen as quite peripheral.
Otherwise I guess with Bolasie back plus Lennon, Lookman and Vlasic who can all play on the wings, there is little room in the team for Mirallas and with supposedly Galatasaray and Olympiakos interested in him then we are probably looking to offload in January.