#3 Mourinho needs to change his system
The way Mourinho set up was too negative. You would expect Manchester United to come at Brighton and press them high up the pitch and get in their faces. You would have expected that but the team that was doing this was Chris Hughton's men.
If United want to beat these smaller teams, they need to set up in the right manner appropriate for the team they are facing. You can't set up against City and set up against a team like Watford in the same manner, can you? Every team is different and cannot be addressed in the same manner especially from a tactical perspective.
What next for Manchester United? Well, they face Spurs at home in their next game and it will be interesting to see how they react to this defeat and how Mourinho will react. But this loss will give smaller teams more hope in so much as they can beat Manchester United if they try to implant the same strategy that Brighton displayed.