A train to FC Barcelona comes only once in a lifetime. MAtS seems like an ambitious guy, so if Barca comes knocking, I'm sure he'll respond. Yes, he's a Gladbacher through and through, but Barcelona offers so much more than Borussia. Money aside, he will have the opportunity to train with the best players in the world. More importantly, he will play in the Champions League, every year. And Barca will get at least as far as the quarterfinals, every single year. I'm sure that MAtS wants to replace Neuer as the first choice in the national team eventually, but first he needs to solidify himself as the back-up. Move to Barca would certainly help him achieve that. If Barca offers good money, I doubt Borussia will want to stop their homegrown player from seizing an opportunity of a lifetime.