Agreed. Jamal wasn't the same player after his injury. Fans speculated that he was going less than full speed to protect his NFL future and his subsequent career seems to have validated that belief.
The conventional wisdom is that a player won't be his old self until his second season back from surgery. Think about Nick Chubb in 2016 and Nick Chubb 2017. While you're at it also think about Shy Tuttle and Quarte Sapp. Don't be surprised if they don't have big seasons.
I remember telling people that Travis Henry was our best rb. After 1999 turned out to be a disappointment, some people were saying that Lewis was the worst first round draft choice ever. I told them that it was his second season back from surgery and he was going to tear it up his rookie season. Just following conventional wisdom is all.