If the relentless stream of praise emanating from the desert is any indication, Palmer might be underselling the potential of the No. 86 overall pick in last year's draft.
"His receiving and ball skills are second to none," Keim recently raved, via ESPN.com's Dan Graziano. "I mean, probably the best receiving back I've seen."
Does that include Faulk, commonly regarded as the most effective receiving back in NFL history?
"A lot of people have compared him to Marshall Faulk, and our coaches had Marshall Faulk in Indy," Keim explained. "I think he's very similar in some ways athletically and in terms of ball-catching skills to Marshall."
Venerable offensive consultant Tom Moore and head coach Bruce Arians are in a unique position to draw the comparison between Faulk and Johnson. As the Colts' offensive coordinator and quarterbacks coach, respectively, during the 1998 season, they witnessed the dynamic dual-purpose back up-close as Faulk exploded for a league-high 2,227 yards from scrimmage.
A wide receiver when he entered Northern Iowa, Johnson retained all benefits of the position when he rocked up to 230 pounds and moved to the backfield.
Three games into Johnson's career, Arians already had him lining up out wide and in the slot as a runner/receiver hybrid. Arians was actually far more creative with Johnson as a moveable chess piece before the rookie was thrust into the workhorse role in November.
"I don't think there's a back in Cardinals history that can do the things David can do," running backs coach Stump Mitchell said earlier this month, via The Arizona Republic. "He's going to put up numbers and the guys on the other side of the ball, there's nothing they can do about it. He's also blessed with a heck of a play caller in Coach Arians."
As a rookie, Johnson became the first player in 16 years to average more than 12.0 yards per reception while gaining at least 400 rushing yards and 400 receiving yards, according to Chase Stuart of FootballPerspective.com. Johnson also led all running backs in percentage of receptions (58.3) converted to first downs.
"He's got rare and unusual skills I've never seen in a back, where he's got an erect running style, yet at the same time he has tremendous lower flexibility and lateral quickness," Keim explained. "So that's a weird combination, because usually those taller, upright guys are kind of straight-legged and stiff. This guy's got an unusual knack of being able to pick and slide and do some things laterally."
"Man ... people don't know," tight end Darren Fells said, per Graziano. "But they're going to know."
"I'm afraid to say it," coach Bruce Arians offered reluctantly, "because then he'll get hurt."
After just one NFL season, Arians stood in front of the assembled media at the NFL Scouting Combine and acknowledged that Johnson has a chance to develop into "one of the all-time best" running backs. Mitchell firmly believes his star pupil is bound for the Hall of Fame if he can stay healthy and motivated.