Marcelo is great in attack, but positionally he's utter crap. He's the kind of player that seems flashy when he has the ball and seems he's very good and indeed he does good things when he participates in the attack, but for some reason the team always ends up unbalanced when he plays. Playing modern football is very much based on positioning, and Marcelo can't understand that aspect of football. Hence why I see Mourinho having problems with him or trying to change his style of play. Another solution would be to put him as an alternative to LW, as he really has the skills to play there.