Like I said, his starting position was exactly what ederson does, people who look at keeping in the traditional way will say its a poor starting position but Pep demands it, can't call him out for something Pep insists on. the entire high backline relies on him being in a poor starting position to sweep.
As I said, his error was he was too slow to react to the play and backtrack, it's a minor error really but it's costly when it's punished like that and looks ridiuclous.
He can also justifiably ask why the fuck did our defence let Djenepo have all the time in the world 20-25 yards out to pull off a casual chip, if walker engages as he should, he doesn't get the opportunity to do that.