Forlan, morientes, perez, sandro, falcao, bailly, navas, soldado, reyes, del horno... just off the top of my head.
All well established la liga players who couldn't do it in the premier league.
I get your point but alternatively there's (off the top of my head) the likes of Aguero, Costa, Torres, Fabregas, Alonso, Toure, Zabaleta, Sanchez, Silva, Corzola...
Marco Alonso, Azpilicueta (via Marseilles), Mata, Pedro (to an extent) and a fair few more I am probably not remember; there's GK such as De Gea and Courtois.
Until he plays it is hard to judge and obviously he didn't flourish at Barca, but he was very good at Valencia - why he moved to Barca - so let's be positive.
With regards to McCarthy, well he's got his own injury concerns and issues to get over so I doubt that he will have an automatic place in Silva's XI or bench.