For a speedy defender, he lets too many crosses in.
In Pep’s system of 2-3-2-3, where he is the right side of the first 3, he is being asked to play more as a midfielder. He is NOT a midfielder. He has poor touch, he flies into silly challenges, he overcommits, he doesn’t have the rain for the pittance doesn’t have th technical ability to seamlessly move forward with interplay.
All that said, I think the midfield part of his game is improving, albeit possibly not quick enough to cover up for his lapses.
In that position (right side of the first defensive line of 3), if he loses the ball, he is immediately putting the back 2 under extreme pressure, usually causing one of them to cover the left winger. Teams already know he is weakest technical player in the team, gets caught out of position an awful lot, and is probably the weakest defender of the back 5, so he gets targeted.
However, he has had some positive forward play in recent games, got himself into good positions, and even played a few decent passes. I don’t think it is a shocker that the full backs in a team are often the least gifted players, but it shows itself a tad more dramatically in a team so chock full of technically gifted players.