Brazilian here who has followed his case closely. Sorry but he just used Spain to go to the World Cup. Don't believe that crap about him feeling Spanish or having a connection because this is where his football developed. I'm not bitter at all for him not playing for Brazil mainly because I do't like his character but there are a few things I want to air out.
1. When he was called up for Brazil he accepted and his family did interviews with Brazilian TV stating how happy and proud they were. He himself stated the same thing when called up for Scolari's first set of friendlies.
2. When he wasn't called up for the Confederations Cup, he senses that he will not make the Brazil WC squad and starts the BS about Spain. He then goes on to say a series of things that he eventually contradicts like how he feels Spanish and Spain gave him everything in football and he owes them, etc.
3. After the World Cup flop and his move to Chelsea, he speaks about still being, loving, and feeling Brazilian. Talks about learning to play footall in Brazilian streets which was what made him different etc.
Long story short, it was a rash decision he made to go to the World Cup and I feel he probably regrets not waiting. I personally believe he doesn't really have interest to play for Spain anymore hence these "injuries" and not being totally committed.