Hate to break it to you but Singletary is literally one of the smallest and least physical RBs in the entire league. Bottom percentile across the board.
https://www.mockdraftable.com/player/devin-singletary
He was on one of the highest powered offenses in the entire league facing light boxes and getting carries on draws and designed misdirections and left so many yards on the field. Constantly chased down from behind. Just small, slow, weak. Absolutely useless between the tackles.
Damien Harris is a much larger, faster, stronger back that can hit between the tackles. Just a competely different type of player. So much better.
https://www.mockdraftable.com/player/damien-harris
There's a reason the only team that wanted Singletary was the Texans for 1 yr as a backup... the starting running back for one of the most high powered offenses in the NFL, just no interest in him.
The entire NFL knows it, he stinks, he'll never crack 1k rushing in his career. You won't hear from him again, he'll be irrelevant now that he's off the Bills.
We got massively better on the ground today.