Ancelotti did not include Nkounkou in the matchday squad that lost 1-0 to Leeds United last weekend, even with first-choice left-back Digne ruled out of the encounter.
The 27-year-old is expected to be sidelined for up to two months and his countryman Nkounkou has been presented with an opportunity to potentially earn an extended run in the first team.
Ball has issued advice to Nkounkou to self-analyse his game and seek Ancelotti’s guidance on what he should do to earn a more substantial role in the senior squad, with the former Everton star also urging the 20-year-old to keep putting the hard yards on the training pitch
“Nkounkou needs to do more in training, need to ask questions and find out what he is lacking”, Ball wrote in his column in the Liverpool Echo.
“I’d be looking at myself and if the manager pulled me to one side, I’d be asking him what he wants from me.
“What do you want me to do in training or how do you want me to play?
“Ask questions and find out what you’re lacking, because it’s really surprising at the minute.
“Nkounkou might not have started and that’s fair enough, but not being in the squad suggests he’s not doing something in training.”
Ball feels Nkounkou has done well with the opportunities he has got so far in the season and backed the young left-back to push harder to earn Ancelotti’s trust again.
“From the outside, we feel like he’s done a good enough job with his opportunities, so he needs to be asking questions and working hard.
“There’s an opportunity with Lucas Digne being out for a few months, but he wasn’t in the squad [against Leeds].
“There’s something not right, but Carlo sees these players every day so he knows more than we do from the outside.”
Everton have an away encounter in the Premier League on the agenda next, at Burnley, and it remains to be seen whether Nkounkou will make the trip.