Not easy to prove but if look at Lennon's. and Eriksen, when he was on the left, both were too far infield which made the switch out to their wide players easier. If a well positioned CM is holding then they can get wider and nearer the wide receiver thus making the pass out More difficult and if they do receive the ball then they can be put under pressure out wide earlier and in a less threatening position. Note the number of fouls Chelsea mids commit niggly fouls away from their own area, without getting booked.Would a Carick like DM have saved any of the goals tonight? Chelsea were great at stretching the pitch. Switching flanks quickly and getting space down out right - our clear and obvious weak spot.
Also, when Hazard played the one two, a good DM might allow the CB to cover the run as the DM is covering him in the CB position. I think Carrick would have been in front of Drogba, I think who played the one-two with Hazard.