Think he could be the Argentine Moyes. Had the best player player in the world not named Ronaldo, Messi or Neymar for the last three years and won feck all, got to one paltry final, despite having the cup finals and semis at home last year, and finished a distant second at best in the league. He would have already been sacked before Mourinho at United.
He could come and do great, but he wouldn't get away with his mode of working at Spurs at United. You can't go into a season happy to play some nice football, nab a golden boot and not compete for anything, even be willing to essentially throw the cups, at Old Trafford. Can you imagine having only won two League Cups in the Premier League era and having a manager who views winning anything with almost contempt?