A bad start for Chelsea is more significant than a bad start by other title challengers. Mourinho's title winning teams always win from the front, go top of the table early and stay there. He's never won a title by making a late run. He hasnt often had to do that, but its not something he's temperamentally suited to doing. When he isnt winning he makes things worse, makes excuses, finds others to blame etc. Alienating the medical staff is one thing, hanging the captain out to dry is another. Last season he might have made exactly the same half time substitution but it would have been explained as an injury.
The title isnt won in autumn but if we can maintain the gap for a few weeks, it could be decisive as far as Chelsea are concerned.