Thats exactly what I mean red, and you said it so briefly

He isnt playing bad perse, but injuries hindering means he is playing in a considerably more subdued capacity then his usual Sevilla/Schalke one.
Plus, Juve is a very big move for him, so so far, in the games he has been healthy enough to play (which has been few because his progression has been hindered by constant injury), he has played rather cautious as you said. Thats what I meant with taken his quiet role. He is keeping himself in a safe mode, before he gets comfortable with the team. THEN we will see what he is really made of. Which as you said, a damn good DM.
MK_Khan, you are also correct, but its beyond his control, I cant say I have been dissapointed or impressed, because he has played way too little, and has been hindered too much from injuries to judge him. He started with a niggling injury, then takes time to get back in match fitness and play a little, then a big 3-4 months injury, and only now yet again he is back to trying to get back to match fitness again, not fit enough to handle more then 60 minutes, needs more time.
His aggressiveness and mobile work rate will come when he has had considerable amount of games and gotten in a comfort zone with the team. So far there hasnt been any time for that.
And him being "overrated" or his performance being overstated, is only natural, because ALOT around here werent only against the principle and point of the signing (which I agree with), but also called bad player this or that etc. So if they expect so little for him, then his calm competence can only suprise them and be seen as going up for him (went from harshly underrated in a way, to what you perceive as being overrated). When its really just barely his normal standard yet, because of due to his unfortunate injuries. He hasnt had a lucky start.