I don't think the club fought so hard to keep him, he was good but never lit up La masia like Dongou,Sandro and Munir playing for Juvenile A, and also of all the other three prospects, Sanabria was the only one who could not play on the wing, he was an old fashion number 9.
What? Prior to leaving Barca he was the main man on Juvenil A and Munir and Adama were his support men, and the three of them dominated, with him usually being the savior. He was also the first one to get minutes with the B team because he was so far ahead and that was around the time he decided he was too good to play for a "B" team. Him leaving was the moment Munir went from being a really good frontman to exploding on the scene and destroying everything. Apparently Munir was comfortable as striker, too. Who would have guessed.
And I don't recall who said it, but he's on Roma's bench now, not Sassuolo's.