So the news wasn't good, with David Johnson (likely) sidelined for many weeks and many games because of a dislocated wrist. Bottom line, this isn't replacing a guy who by default ended up at the top of the running-back-by-committee depth chart. This is arguably the best running back in the league. He comes out of the lineup, it makes a difference.
The Cardinals have to find a way to run the ball going forward. That will be some combination of Andre Ellington and Kerwynn Williams, I'm thinking. Reports that the Cards are signing D.J. Foster from the Patriots practice squad makes sense; Foster could in theory become a punt returner. The Patriots tried him a little bit there in preseason (Foster did not return kicks or punts at Arizona State.) If Williams is playing a lot of running back, I'm not sure he'll stay with such a big return role. J.J. Nelson is an option back there, or Brittan Golden. (The punt return job can't help but not be settled, right? It's one thing or another.) Elijhaa Penny would be an option as a big back, although Sunday, after Johnson got hurt, Williams was still used inside on a couple of up-the-gut short-yardage plays.
The offense could look a lot more like the 2013/2014 model, before Johnson was drafted and before Chris Johnson's resurgent 2015 season. The Cardinals didn't run as effectively as they wanted to those seasons, but they made it work and they won games. Now, it's about making whatever you can work, and hope Johnson can return late in the season for a playoff push the Cards still hope they can develop.