He was excellent against Madrid in the league at CB, that was what 2/3 games ago?.
He'll be fine, literally last player I'm worried about of the players we paid money for last season.
If xavi wants a Defensive RB and think that's him, he'll learn to play the position even better next season, but we will need another option off the bench, if we sign a starting RB, he'll be rotating with Araujo & Christensen next season, they will all play about the same number of games, with Kounde filling in at RB when we want a more defensively solid backline.
Pep is playing 4 CB across the back these days, maybe xavi knows what he's doing with a more defensive RB if that's where he's play long term. IF.