#2 Alexis Sanchez's impact
When an already great team procures the best player from an average team, math indicates that the already great team can only get greater. Who are we to question the laws of mathematics?
For years, Alexis Sanchez has carried Arsenal on his back - he had absolutely no assistance from the likes of Mesut Ozil or Aaron Ramsey or Olivier Giroud. Football doesn't work like that; it is the individuals who win the team plaudits.
Anyone who has watched the game knows that players take no time to settle into a new team. And being the humble guy that Sanchez is, he doesn't get annoyed when his teammates fail to deliver the right pass to him. Combined with his clearly-not-waning age, Sanchez is Mourinho's final piece in this puzzle to victory.
Remember when some people were worried that Manchester United's No.7 shirt has been jinxed since Ronaldo? They must be feeling so stupid right now.