DonAndres
Wild Man of Borneo
As long as they can walk del Bosque will take his selected midfielders that he took to the last four tournaments. Even not fully recovered he took Cesc(hamstring) Iniesta(hamstring) Torres to Worldcup 2010. Despite Puyol having surgery he wanted him to stay with the team at Euro 2012. Good form or not he will probably take him to Brazil as long as he isnt having surgery this time next year. He waited till the last minute for Villa too and in the end didn't carry a replacement, just gave the number to Pedro, just like he didn't name one for Puyol. In any case why hypothesize about injuries when Thiago himself could get injured in England as happened the last two seasons in a less physical league.
Be that as it may it's not a completely impossible circumstance. VDB is conservative to put it mildly but if Xavi really were injured I bet he would feel much more compelled and comfortable bringing in an excelling Thiago fresh off a great debut season with United rather than a patiently waiting Thiago who's stuck on the bench at Barca and considered "still just a prospect". It's FAR from guaranteed that Thiago will even get considered but it's not as impossible as some people make it out to be.