He's had a terrible season..
But it would be very typical of Juve to sign him on the cheap and turn him into a truly great player.
Cannavaro's stint at Inter before he joined us in 2004 was pretty mediocre and unsuccessful. I know, I know, one can't just deduce from it that Ranocchia will do well at Juve, but I can definitely see it happening and it would be very typical.
Also, since I've lost all faith in Isla, I say go for it.