Qwiss different styles of injuries though.
Odegaard had a serious ankle injury that was likely bone and ligament. Once those are healed you don't drop off because it doesn't necessarily impact/degrade the muscle, though tendinitis and other issues may arise in the future.
Saka is struggling with injuries to major muscles that bind his lower body together. If his hamstring is shot, he'll be overcompensating with other muscles and putting them at risk. He'll also have stiffened up considerably and in doing so last his burst/pace.
I think a better comparison for Saka would be someone who's done their ACL.