Lower-body injuries. He started out 2021 looking the best he had in years. He got his playing weight down and hasd more spring in his step. Only those who dislike the player deny that, but the evidence (numbers) is there. That October, he suffered a knee strain. He hurt his ribs in the next game. Then, he suffered another knee strain in early November and a PCL tear in later November. Just because he played through those injuries made it to where some fans expected those injuries to not take a toll, especially with most of them to his lower body. He probably should have been shut down. The next year, he also started out decently before suffering a knee sprain in October.
Now, no injuries show up in the report on him in 2023, but all of those lower-body injuries may have added up and contributed to him hitting the RB wall. I would expect this year, even if he is somehow revitalized early, for his body to not hold up again because he's just reached the point where that happens. Players want to continue their careers, but sometimes the body just says no.