Three weeks ago Chelsea were in disarray defensively. They let three goals in against Southampton to squander a victory and were three goals down inside 27 minutes at West Brom.
Frank Lampard's exceptional work in the summer transfer market looked like it was going to be undone by a defensive unit that couldn't provide the platform his devastating new attack needed.
But fast forward to today and the Blues have kept five straight clean sheets and look to have finally found a settled backline.
At the core of that is Kurt Zouma, who has played in all five of the defences that have kept clean sheets in games against Sevilla, Manchester United, Krasnodar, Burnley and, on Wednesday night, Rennes.