Silva has been injured this year and has struggled to recapture the form of last year. But last year I felt he was one of the best midfielders in Europe, so on that basis, I guess he's edging it for me. There's no doubt Mata has been the better midfielder this year, but I think much like Silva, Mata is enjoying a glorious second season, so I think Mata almost has to finish the season like he's begun it to match Silva's feats of last year.
If they're both fit, I think next year will be more revealing.