Top Stories RB: Andre Ellington, David Johnson, Stepfan Taylor, Kerwynn Williams, Marion Grice, Paul Lasike, Robert HughesGrade: 3 starsThe Cardinals have had less-talented running back groups in their history. They’ve also had groups that were more proven. Entering this season, Arizona’s group has combined to rush for 1,938 yards — in their careers — with Andre Ellington’s 1,312 leading the way by a large margin. As of now, the expectation is for Ellington to once again assume his role as the number one option. He had a down 2014 after playing most of the season hurt, finishing with just 660 yards and three touchdowns on the ground and 371 yards with one score as a receiver. He’s healthy now and figures to look more like he did as a rookie, when he was a dynamic playmaker, than he did as a sophomore, where he appeared rather limited. The depth behind Ellington is unproven. Many believe Johnson, a third-round pick from Northern Iowa, will emerge as the team’s second running back — and maybe even challenge Ellington for the No. 1 role. Noted as a three-down back by the team’s coaching staff, it should not be long before he starts receiving carries. The 5: Takeaways from the Coyotes’ introduction of Alex Meruelo It helps that there is little else of note on the roster. Williams was the only Cardinal to rush for 100 yards in a game last season, Grice ran for a touchdown in the playoff game and Taylor has proven to be reliable. Yet, none have given any indication that they could be a team’s featured back, and that leaves the Cardinals somewhat thin at the position. Playing behind a revamped offensive line, there’s a better-than-good chance Arizona’s running backs will find more success in 2015 than they did in 2014. And who knows, perhaps better blocking will allow each of the team’s runners to look better than they have in the past. But until proven otherwise, there are some very understandable question marks about this group’s ability to stay healthy and produce. Derrick Hall satisfied with D-backs’ buying and selling Comments Share Grace expects Greinke trade to have emotional impact As training camp nears, we thought it would be a good idea to take a look at the team on a position-by-position basis, grading each group on a five-star scale. So, how does the team look? Former Cardinals kicker Phil Dawson retires The Arizona Cardinals won 11 games in 2014, and if not for an incredible amount of injuries very well could have had an even more successful season.Look around, though, and you’ll see varied opinions on how they will fare in 2015. Some view them as a contender, a team that will compete for a Super Bowl if it can have a little luck in the health department. Others believe last year was a bit of a fluke, that they are destined to take a step back.