Scott Brown: Celtic display was ‘unacceptable’

The Hoops were losing 2-0 at the interval through a Lionel Messi double, but Moussa Dembele had a penalty saved by Marc-Andre ter Stegen when it was 1-0 for the home side.
However, the Scottish champions capitulated after the break and Messi added a third for his hat-trick, Luis Suarez a double with further goals from Neymar and substitute Andres Iniesta.