He sits much too deep trying to bolster and coordinate their possession. Nothing really helping on the offensive end, which granted isn't really all that much of a problem for them. Where he is the biggest liability is defensively. Much too slow and not good enough defensive positioning to break up counters or slow down the opposition.
They really need a true CDM. They are extremely leaky at the back, don't have the best goalkeeping and overall poor defensive organization.
And couldn't they get someone in January?
They will have to. But from here on out they will have to score 3 or more each match against the rest of the CL challengers.