I can understand Juve cashing in on him but swapping him Lukaku that has to be the dumbest swap ever. Can you imagine that pile of shit trying to play Sari ball it would be embarrassing he has the touch of a baby elephant.
On the surface it seems like a bizarre move, but I think Lukaku is a much better player than he's shown at United and one of the key things Pep's staff live by is that players can always improve their basic technique a lot if they're taught properly - no matter how old. Abidal is the example spoken about in Pep Confidential, where he was a physical lump when he arrived and totally changed his game.
Lukaku's touch used to be better, 2 1/2 years playing Mourinho-ball barely being involved in games brought it down to the level it's at now, and if Sarri & Juventus coach him properly I wouldn't be surprised to see it improve drastically.
One of the things that's always been weird about Lukaku is he has an incredible cross when he ends up out wide. In Belgium's best games in the world cup, Martinez put him on the wing and he was unplayable, way too big for any fullback to deal with, and running in behind he caused havoc. Sarri's #9's get a lot of license to go out wide because the wingers come in, and especially with Ronaldo that will be the case, so maybe that's one reason he wants him.
I don't know if he'll ever be one of the very best strikers in the world, but given some proper coaching, playing in a well coached side with his confidence back and I think there's a decent chance he makes United look like idiots for selling him in 18 months time.