You are correct, it's funny how time plays tricks with your memory. I checked on wiki and can't believe how few games Ruggerio played for us and also had no recollection of Lawrenson joining then who apparently took Sayers place later on forcing him to leave?
20 Aug 1977 Southampton v Brighton and Hove Albion 1-1 League Division Two
I remember there were 3 debuts including Sayer and Ruggerio and that there were people being led out in front of us by police for what seemed the whole game.