Ngog is a doubt for the game at Turf Moor after picking up a back injury in the Europa League game with Athletico Madrid.
"Ngog was really tired. He had some knocks and a problem with his back, so I was talking with the doctor at half-time. He told me he couldn't play 90 minutes," said Rafael Benitez.
"We will consider a number of things but it's too early. We have to train and afterwards analyse carefully."