I don't think it's necessary to have one of them playing in front of the other, Cabaye did well in that role for a bit last season, but I'd rather he play a bit deeper. The problem is he plays too deep, it should be a DM with those two sitting in front, Sissoko can push forward and Cabaye can spray it around. It's just baffling Pardew hasn't moved Sissoko back a bit, the fact Deschamps openly laughed at the suggestion of him playing attacking mid tells you everything.