Mustafi struck last night and later admitted reverting to a back three had taken some adjusting to.
He told BT Sport: "We played with a back three, a system for a long time we didn't play. So we needed our time a little bit to get the rhythm in.
"In the first half we didn't do as we wanted. I think we came out better in the second half, had better rhythm, better passing.
"We need to stay calm. Everyone wants to show and give everything, sometimes when you are over-motivated it's difficult to deal with that.
"But I think at the end of the day we need to stay calm, play our football, believe in ourselves and then in the final third try and do it a little bit more intelligently with more accuracy with our last pass."