It's a technical error though, isn't it? I mean they are taking shots at him in training and surely he's saving them? He'd save that 99 out of 100, but the concession and the overall play on that goal was pathetic from all involved.
You could stick a Buffon shirt on a mannequin and it would probably make a better save attempt. The whole mentality of the team today was to do as little as possible, classic Juve bulk game management, which I don't think Sarri is particularly encouraging.