Mata should have made his firm decision to leave Chelsea. I think he just donated his world cup place to Isco. I do think Isco would have gone to world cup anyway, but it was a question in place of whom, Cazorla, Navas, Silva or Mata himself. I was thinking Silva since his form has dropped, and never back at the levels required, although he started the season well.
Now, I think Mata has almost no chance. With Koke and Thiago also being in the frame, it's a bit of lack of ambition from him.