He was impeccable against Juventus, but other than that, I think I can only pinpoint a substitution-appearence against Verona where he came in and made significant, positive contribution. Other than that, he's been dire to outright catastrophic, and it's pretty safe to assume that we'd still be in the Champions League if not for his mistakes. Futhermore he's only gone and gotten injured in the run-up to a key part of the Scudetto-deciding stretch, and there's not a whole lot telling me that he'll suddenly come back and be a key contributor to the squad after a major knee surgery.
That's what we've been paying 6.5 million a year for.
Along with Kolarov and to a lesser extent Young, he's proving to be exactly the kind of transfer we don't need - old, experienced, transfer-fee-less but ultimately quite expensive to have on our books. I'm glad Conte has changed his ways and replaced him with Eriksen, but it took way longer than it should, and stands as a testament as to why you don't give a coach (and especially someone as hard-headed and stubborn as Conte) control over the transfer market.
If there's any silver lining to Vidal's presence at Inter, it's that.
If you're paying someone 6.5 million a year to be a good cheerleader, you're doing something wrong.