Fatigue

We've played 38 games so far this season (including community shield, super cup, club world cup) and here is the number of appearances a few of our players have made

Hazard - 38 (31 starts 7 sub appearances)
Torres - 37 (32 starts 5 sub appearances)
Mata - 36 (32 starts 4 sub appearances)
Ivanovic - 32 (32 starts no sub appearances)
Cole - 30 (29 starts 1 sub appearance)

(source: espn)

Squad depth


Oh and Just to highlight the point Cech has only played 34 games which means at least 3 players have played more than him this season

Obviously through the course of this season we'll have played an abnormal amount of games even compared to other seasons, but I think this goes to shows that we need to utilise the whole squad more than we have been doing so which is where I give credit to Rafa as he has done this (albeit frustratingly) more than RDM ever did this season.