He's performing alright for a la masia player. The real issues at defense stem back to not being able to properly replace Alves, Mascherano, Puyol (and Pique, Alba now) ever.
Umtiti crippled, Lenglet shit, no good RB in years. If this wouldn't look so depressing then someone like Araujo filling in would be perfect. Also he's no RB anyway, but that's what happens if your RBs are Roberto and Dest who fills in as a forward as well because the only fast winger in the entire squad is Dembele. Poor planning all around.