I have little interest in the Bills trading for a RB when the real issue is the OLine, but this take isn't really fair to Barkley.
He had ~ 1500 yrds from scrimmage in his second season with no QB behind a horrific OLine when he was the only threat on the field and every opposing coach and player was keying on him every snap. That's a pretty galdanged impressive outing to call it a "decline".
He tore an ACL at the beginning of the next year, which he was just recovering from barely 1 year later when he stepped on a linemen's foot and hurt an ankle he's been playing through all season.
Barkley's a stand up kid, a ferocious worker and a high quality human being. If he ends up getting out of that gawdawful mess in New Jersey and finds himself on even an average offense next season, I wouldn't be at all surprised to see him win some sort of Comeback Player of the Year award.