Tough one, a joint award? That way no one gets left out!!!! Both have strengths and weaknesses that dovetail nicely, we both miss them when injured, both have weighed in with massive performances.
Yaya has stepped up with goals this a plenty and match winning performances, Silva has had plenty of great performances, his hull one being a prime example! he hasn't scored as many goals as he should! but he supplies others and oils the gears of our attack so well. But for his injuries, he'd be up there alone.
But the whole team has found a new gear, Garcia, Fernand, Kolarov, Dzêko , Aguero, Nasri, Kompany have all had spells of greatness and/ or improvement .
So for me a joint award, but if I have to choose, Yaya.