He would get in fights with Suarez and Messi. Dude is as ruthless as they come. If you walk or give a half assed effort he will sub you out. I recall there were a couple of Milan players that he got in a feud with.
Suarez, yes. But at this point, even the burgermeister knows his own bacon-cheese Pocito away from obese. He might pout a lil'bit just for good show but inside, he'd be thankful coach for letting him support the team from the VIP section.
He wouldn't fight with Cap. Dude is not retarded. He knows how Messi plays and why would he try to suddenly turn him into Eliud Kipchoge. He'll do exactly what a top coach would do and try to build an effective attacking system with fast electrons who can actually finish, offering passing options to Leo's perfect aim, along with good forward build-up players to bring the ball up in the third where Messi is deadly.
This way, Messi can still do his Adam's Family passeo on walkabout creek and have fun while delivering off the charts performances.
Barto is the piece of shit who doesn't wanna see this happen. Besides, he only hires YES man and El Gato Fato only says yes ad una buona porzione di pasta _ and nothing else