I don't understand all the doom and gloom predictions. It's one player, just one. Pep's not kicking out deserved players, he's not disrespecting anyone so far. We let go off two players (Gomez, Tymoshchuk), we bought two players (Götze, Thiago). As long as Thiago is working just as hard as the others and playing just as good if not better, it won't be a problem when he starts. If Pep treats him different, starts him despite playing worse, then we have a problem, but I doubt that will happen. Bringing two or three new players in after a successful season isn't something controversial. You need fresh blood, new ideas, tweaks in tactics to stay unpredictable and keep the excitement up, keep the whole squad motivated. Everyone needs to work hard in pre-season, no one can relax and be sure of his starting spot and if there is one player who isn't happy with his situation, he will be allowed to leave, just like Gomez. I don't understand the concern for Emre Can either, he's 19 years old and many doubt he'll ever be good enough to start for Bayern, Thiago is clearly a way bigger talent. He can go on loan for 2 years like Kroos, Lahm or Alaba did for example and still is younger than Thiago now when he returns.
/edit:
feck, sorry, edited Tymoshchuk above instead of Mandzukic, of course he's still with the team