Traditionally Chelsea have a change of form in the winter months. I've always put it down to a higher number of players who grew up playing football on hard grass surfaces. When the ball stops bouncing and rolling as well the team struggles. Colder weather can lead to a higher rate of muscle injury too. If Costa picks up an injury Chelsea are back to last seasons form.
Traditionally Chelsea have a change of form in the winter months. I've always put it down to a higher number of players who grew up playing football on hard grass surfaces. When the ball stops bouncing and rolling as well the team struggles. Colder weather can lead to a higher rate of muscle injury too. If Costa picks up an injury Chelsea are back to last seasons form.