2. Roberto Firmino must play up top
Apart from the game plan staying the same as in the Arsenal game, Roberto Firmino must play up top for Liverpool against Manchester United as well. He might not have the physical presence of a Christian Benteke but his movement and certainly his finishing, as seen against Arsenal should make him a sure shot starter.
The Brazilian scored a couple of wonderful goals against Petr Cech and even did well against Manchester City and Chelsea. Maybe playing in the big games gets the best out of Firmino and if he can bag a goal or two against Manchester United, no one would complain about his slow start to his life at Liverpool.