United endured one for their worst campaigns in Europe last term.
Vidic said: "In Europe we've had so much success in recent years - we've had three finals, a semi-final - and maybe we relaxed a bit last season. We were punished last season and we can't allow that to happen again. We had a few injuries last season too. I hope everyone can stay fit this season. The young players can learn from last year, so I'm confident we'll be better this year."