Hummels is laughably overrated. Like Luiz he's incredibly gifted with the ball at his feet, he has his fair share of "monster" games where he destroys everything in his path but he's simply too error prone. Because he doesn't have extravagant hair/personality, play(ed) for a club that's where every error is scrutinized & is in a relatively quiet League his frequent mistakes are swept under the rug. Dortmund were so bad defensively last season that they flirted with relegation yet his reputation has largely gone unscathed. His performance against Wolfsburg in the German Cup final for example is one of the worst you'll ever see from such a highly rated defender. He isn't a bad player but Stones will be far better in the long run for me.