Last two monts of the season, Vidal's defensive performances were significantly improving. Wich seems to be mainly related to recovering from his injury and finding form IMO.
The final big games in serie a, and the Cl games against real madrid, he was top. Against Barcelona the first half, the entire team played like they where having a butplugg,except Vidal and Buffon. Buffon kept the score at 1-0 instead of 4-0, and Vidal was the only single player that showed up, and was holding back half their midfield on his own.
Offensively, he was taking chances again, but in a very wastefull way. And as i've said back then, i cant care less about vidals offensive performance. I care about what he defensively does, cause thats where i value him very highly