Tbh he gave the ball away a lot last season as well, it is one of the things he needs to work on. Probably also the reason why he is still largely played as an attacking midfielder with Barry/McCarthy behind him to tidy up rather than the CM role that Roberto says he sees as his eventual best position.I didn't mean that in a super negative away, I know he's lacking match practice at the moment, there's no doubt he'll get back to holding the ball as well as he did last season.
But Martinez is pretty relaxed about young players making mistakes like giving away possesion, one of the reasons Barkley has seen more game time than he ever would have under Moyes, Hodgson and probably Mourinho too.