For my money the fault of goals so far:
Southampton 1 : Lucas primarily.
City 1: Moreno slow reactions and should have cleared.
City 2: Skrtel, basic failure to keep the defensive line,
City 3: Lovren, too much space created by not moving with Moreno as he was pulled wide.
I don't quite understand why our players are making such basic errors? Arguably City 1 and City 3 are to do with a new full back bedding in, but the other two are inexcusable.