Even though England is superior in terms of player material, Senegal strength should not be underestimated. Senegal is slowly reaching a good level even without its star player Sadio Mane who is currently injured. This match will be fierce because a number of Senegalese players such as Edouard Mendy and Kalidou Koulibaly already have experience playing against English players.
England still rely on names like Harry Kane, Bukayo Saka and Marcus Rashford to damage Senegal defense. Senegal will try to tighten up the defense to frustrated the English players by relying on the occasional counter attack.
I think you shouldn't consider Senegal to be that great when Mane is missing. Mane is the type of player that can get the ball and create a chance for himself out of nothing and score. Without him, Senegal is not good at all and they will not win. England is by far the superior team, and they were a superior team even when Mane was playing, but without him? They are even better and will stay better for sure.
I just hope that it would be an entertaining game to watch, but I wagered on England with ease, unless we see another huge shocker in world cup which has happened already, then we are going to see an easy win for sure and a good return on my bet.