When you have a 6'3 striker marking the goal post and Azpilicueta marking the tallest guy on the pitch, not once, but twice, and both occasions leading to goals, you can only conclude its down to coaching.
Not sure if many of you remember our 2010 title winning season thoroughly, but we were awful in marking set pieces. The very reason why we won the title on the last day of the season, in spite doing the double against United, Spurs, Liverpool and Arsenal, was down to our poor marking against mid table sides. Ancelotti carried on after Scolari and had us zonal mark in set pieces, when under Mourinho we were very tight in our marking.
I find it very lazy, zonal marking.