Keim isn't alone in that sentiment.
"I can't say after one year's work that he is one of the best," Arians offered, "but he's got a chance to be one of the all-time best."
Arians isn't anointing Johnson a Hall of Famer after 18 NFL games. He's simply pointing out that a well-rounded, three-down back who led the NFL in scrimmage yards from Week 13 through the end of the postseason has a chance to build on that elite production going forward.
Per Next Gen Stats, Johnson recorded the fastest speed by a running back as a ball carrier in 2015. He also launched a 41.5-inch vertical leap at the NFL Scouting Combine last year. He's the rare back who combines freakish physical gifts with natural running and pass-catching ability.
Arians might be reluctant to concede the self-evident in a public setting, but we're not: Johnson is already one of the NFL's premier running backs.