Running back David Johnson only played a few snaps for the Cardinals Saturday, getting three touches -- all runs, for 16 yards -- on the first four plays. He was stood up on his last carry and took a shot, although General Manager Steve Keim said he wasn't concerned.

"It's going to be tough to hurt a 228-pound back," Keim said during his appearance on the "Doug and Wolf" show on Arizona Sports 98.7.

Keim also made one other thing clear: While there might be a feeling like placing Johnson in bubble wrap until the Cardinals get to the regular season could be the best course of action, it is not. "As good as he is," Keim added, "he needs the reps as well." There's no substitute for getting action in a full-speed football game when it comes to getting ready for full-speed football games. That's the reality, risk or not.

Among some of the other Keim thoughts from the morning:

-- After the constant talk the past two camps about the progress of D.J. Humphries (two years ago) and Robert Nkemdiche (last year), Keim was asked if there had been anyone in particular he has been disappointed or frustrated with this camp. Keim said no. The GM admitted that early in camp he might've been frustrated with second-year cornerback Brandon Williams from a consistency standpoint, "but he's picked it up. He's working his tail off. ... He's come a long way."

Keim said he can't think of anyone underachieving, and given Keim's ability to be blunt like his head coach, that's a good sign.

-- Not surprisingly, one guy Keim was pleased about from Saturday's game was linebacker Josh Bynes. Bynes picked up the defense quickly, and Keim likes his range, speed and length. "He's had some success in the past," Keim said, and echoed what has become clear, that Bynes has a shot at the roster.

-- Keim was happy with offensive execution and the physical play from the Cardinals. He was hoping for a three-and-out from the first-team defense after the initial TD (it should be noted the Raiders didn't play starting quarterback Derek Carr), but that's one of a handful of things the Cards can work on this week.

-- There are still many things to improve for Nkemdiche, Keim said. But he did say Nkemdiche is "headed in the right direction," praising his want-to, work ethic and film study.

-- Film study will be important to the top two draft picks, linebacker Haason Reddick and Budda Baker. Both need to keep working on getting their eyes in the right place during plays, understanding what the offense is doing and finding a balance between quality aggressiveness and staying disciplined.

-- Both punters had "extremely live legs" but Keim emphasized it's not just the length of punts that are judged but also hang time, ball placement and such.