I think Silva would get into Madrids starting 11 but I'm not sure about Barcelonas.
Iniesta and Xavi are better than him and Sanchez offers a greater running threat. And he's obviously not going to get ahead of Messi. That would leave him in a shootout with Fabregas and I honestly think Cesc is better.
I think in both cases he would be in rotation. But given the way form changes I can see him becoming a starter. I too think cesc is a bit better right now but you know how players are, a run of poor games and all of a sudden Silva is sat there as the number 1 in the spot. Particularly a player like Fabregas who really can burn brightly for a while then fade for a bit.