With injuries to Danillo, Walker hasn't had any pressure put upon him, and until recently when Danillo was fit Pep was able to drop him/rest him. Now Danillo has to cover at left back, Walker is again playing without the fear of being dropped/rested/replaced due to poor performances.
We need to sort left back out to allow Walker/Danillo to be our right back pair and fight for the position.
And left back is a real problem, Mendy is yet to prove...
1. he can stay fit for longer than a few games (perhaps he's been unlucky having such long term serious injuries)
2. he is actually a decent defender.
The jury seems out on him been our long term left back.
Neither Zinchenko or Delph are a long term solution for left back, Zinc is likely to leave, he's never going to play in his preferred position with the players we have, and Delph is getting on a bit and come June he'll be in his final year of his contract, it will be interesting if we offer him a new deal at the age of 30 for a players who will effectively be a utility player.
Spend big in the summer for a new left back - Chilwell at Leicester would fit nicely, and make sure Mendy, Walker and Danilo get most of the summer off and get a rest.