Mats need to realize he is a kid and at the moment less than Bravo. Count his blessings for being a at club like Barca playing cl and copa and learning.
Just be patient, in 2 years he will be the goalkeeper for the next 10. If he leaves now he will regret it in the long run.
Let's think of this from his point of view then. I mean, the only two keepers his age and better than him are Courtois and DDG. The major difference is that they're getting consistent playing time atm. Courtois in particular wouldn't have ever been this good had he never gone on loan to Atletico.
If MAtS leaves and does good on his potential, the ones suffering will be Barcelona and not him. Sure, he probably won't win trophies or get to share a dressing room with MSN etc, but when he's world class, teams apart from United/Chelsea will be more than willing to take him.
Like Bojan said ATS played 12 games this season, Bravo 15. He starts in CL, Bravo starts in La Liga. Maybe explain that he is in the best club in the world and that his time will come, to be patient a little and work hard? And perhaps also start him in easier La Liga matches?
The only reason as God Serena explained earlier is because Bravo was injured. If Bravo hadn't got injured, the numbers will paint a different story. The four La Liga matches he played wouldn't have happened if not for the injury. And you do realise how if this continues, Bravo will always get 38 matches but MAtS' minutes will be variable based on how far Barcelona progress in a knockout tournament?
And, Lucho isn't changing the fact that Bravo will only get La Liga minutes and MAtS gets CL minutes. Chelsea were smart about Courtois (he's been a star since his Genk days), they realised that he needed playing time and loaned him out and bought extra back-up keepers until Courtois was ready to usurp Cech.