The thing is, he actually does influence the game far more than any other United player. 109 touches and 93 passes against Newcastle. Only Schneiderlin came close to those numbers but he was much further back on the pitch. FWIW, Silva had 91 touches and 80 passes against Everton, but obviously made them count for so much more.
I know the videos above have been taken down, but I actually thought he did well in the first 15-20 minutes. He moved the ball on quickly and had Newcastle scrambling. But then, as Mata started to slow down the tempo, United's entire attack began to lose its bite.
For better or worse, Mata has consistently been given more freedom than any other player in the United side. First in the hole in the 3-5-2, then on the right in the 4-3-3 and now the 4-2-3-1. Everyone else has to stick to their positions whereas Mata can wander pretty much wherever he likes. If only he'd shoulder that responsibility with a bit more verve, I think we'd be favourites, or thereabouts, for the title.
On paper, Depay, Rooney and Mata are three of the most talented players in England. Mata's form is critical to making it all tick, though. So far, he's only given us about 20 minutes in the league. Solve the problem of Juan Mata and you solve the problem of Manchester United, imo.