1) Player fatigue
Unlike a lot of the top teams, Jose Mourinho doesn’t rotate his starting XI that much through the season. As a result, John Terry, Branislav Ivanovic, Cesar Azpilicueta, Cesc Fabregas, Nemanja Matic, Eden Hazard, Oscar, and Diego Costa have played the vast majority of the Blues’ fixtures this season. It also means that his group may be tiring towards the end of the campaign. Fabregas has especially shown this, with his performances dropping off dramatically in recent weeks.