Maybe Sensi could've come on earlier for Vecino. Conte really should have predicted and tried to adapt to the Dortmund 2nd half but whatever, it's all academic now.
What I must say is that Vecino seems poor at performing certain duties you'd normally expect within his role. That's partly not his fault, because all players have their own mould, and Vecino started his career as an AM after all. But players need be able to perform specific instructions that the coach gives them, even if the instructions are a bit unnatural.
A good example is Bernardeschi in the trequartista role he's playing now. It's not natural to him, nor is AM even his natural position, but he's doing as Sarri instructs and he's sticking to the opponents CM very well - see how he marked Brozovic and made it hard for him to do his playmaking duties.
By comparison, there seems to be no indication that Conte is either instructing him to mark any player, nor that Vecino has the sense or tactical discipline to do this if it were asked of him. This annoys me immensely. This is why despite racking up close to Brozovic numbers in distance covered, you never seem to see him anywhere in defense. For all his running and hustling, it's largely wasted on ill-disciplined and disorganised attacking.
Sometimes it pays off, see his great goal vs Dortmund. But he needs to be reigned in on a tight leash, or develop the brains himself to use that running more intelligently in defense. It annoys me that he doesn't seem instructed to defend better.
Based on his physical attributes, his speed, his great gas tank, his willingness to go in for challenges etc. physically speaking, there's no good reason why Vecino can't do what Barella does. Just look at how Barella hounds opponents constantly, like a Medel or Gattuso but with brains and skills. Vecino just... doesn't seem to want to..? If he could spend some of his energy making life hard for opponent midfielders instead of just jogging around all lanky and languid, he'd make himself 3x more useful. Prick.