Let me shock you Manchester United may not win the match if care isnt taking. And the bookmakers are also speculative when it comes to odd decision making. I wont agree that they know more than us.
Real Sociedad is not okay this period and even if we assume that Manchester United is sick then I will be surprised to see Real Sociedad outperform them in tomorrow's game. Their last match was against Sevilla and they lost it, they were humiliated by Barcelona in the last days. Manchester United got a draw in their last match against Arsenal which is very good in the my opinion.
I will go with the team that fails its supporters the whole time, Manchester United!