Has Koscielny missed training?? Comedy of errors gift Chelsea!!

And in my opinion, that is it. Two set pieces, two defensive howlers and two goals….! 
Koscielny, in for Mertesacker, played a part in both and the way he performed yesterday made me wonder if he had been skipping training!! That was not the kind of kind of performance we are used to seeing from him!!
Just recently, Arsene Wenger had talked about the difference between:
‘The Premier League games and the big games”.
He said that yesterdays fixture was definitely one of the latter and yes he was right. It was a huge game between the two top London clubs in the league and the same two who will be fighting it out for the Premier League title come...