It can take players a while to settle down, we've seen it all before with the likes of Bernardo.
What is your opinion of him 1 vs 1 defensively? Whenever I've seen him he's always looked strong in that regard and with the pace he's got, I can't imagine too many can run away from him even if they do beat him initially. We need a pacey left back, Mendy and Zinchenko are too slow and we struggle against counter attacks down that side, especially if Laporte is missing as well.
I appreciate his choice of pass sometimes hasn't been the best this season but he didn't seem to struggle at Betis, so I imagine that's down to his understanding with teammates or confidence like you say.