Mane had covid, he isn’t injured, he will be back for them after the international break. Thiago & Henderson will be back too, I think Liverpool will respond to their humiliation against Aston Villa & beat Everton.
Liverpool can't do with Mane but they can function properly without the rest front three, as they have quality players that can play perfectly in those wings. Liverpool already are not known for suffering two straight defeat simultaneously so the chances of everton defeating them is thin.
The only scenario I see is a draw game that's if everton plays extremely well and brings the fight to liverpool or Mane doesn't feature. He has been very brilliant for them and was a major force behind their winning of the title last season.