The Arizona Cardinals drafted seven players in the 2015 draft. Some will play more than others, but which rookie will contribute the most in his first year?

Last season, the Cardinals had five rookies make at least some visible contribution. This was due in part to a myriad of injuries. A fully healthy Cardinals roster, however, has a very large pool of players, so it is unlikely that these rookies will get as much playing time with more competition.

One rookie, though, will likely get a chance to make plays immediately, and what he brings to the Cardinals can truly be game changing. That player is third round RB David Johnson. Johnson, who looks like he may have the potential to be a major draft steal, bring three important things to Arizona.

First, he has both the receiving ability needed to fit well in the Cards’ offensive system. Current lead runner Andre Ellington, who was hurt last season and unable to be effective, is so important because he is a great receiver. Whenever Carson Palmer or Drew Stanton needed some security on short or screen passes, Ellington could get the ball and make something happen. Crunching some Pro Football Focus numbers shows that Ellington averaged over 10 yards after the catch on negative yardage passes.

The importance of Johnson is that he can duplicate the same versatility if Ellington is hurt. Bruce Arians can plug him in on any play and lose little in the area of receiving. Having a backup running back who can do that while also having a different set of physical tools is a great new way to add to the potential of the offense. It will likely be one the Cardinals look to exploit.

His second contribution is his logic-defying combination of speed and size. Johnson measures up at 6’1″ and 224 pounds. Despite being a big guy, his 40 time of 4.5 seconds was the fourth highest among running backs at the Combine. This is what makes Johnson something of a better version of Ellington.

The knock on Ellington (5’9″, 199 lbs.) is that he isn’t big or durable enough to be the workhorse running back. In contrast, Johnson has the size to become a powerful interior runner, something Arizona lacked ever since Jonathan Dwyer was arrested last season. A young power back for short yardage situations will be a major asset to Arizona.

The last way that Johnson will be able to make an immediate impact is his potential as a return man.

Keim: David Johnson three down RB, will also get a chance to return kickoffs. — Mike Jurecki (@mikejurecki) May 2, 2015

The return game is an area that has killed the Cardinals over the last couple years. Last season, the Cardinals averaged 19.0 yards per kick return, the worst mark in the league. This wasn’t all the fault of Ted Ginn, the Cardinals’ primary return man. The blocking was not effective either.

Any new player who can add some life there will be valuable for the Cardinals. Special teams are sometimes an underrated aspect of the game. If Johnson and the rest of Arizona’s offense can start needing to go four or five less yards per drive, life just becomes easier.

Johnson’s size and speed combo will help him in this area. Sometimes, teams just put their fastest skill position player on returns (see Ted Ginn). Now, the Cardinals have someone there who can both cover distance and get through contact.

Ultimately, Johnson will be impactful because he has a variety of uses. Need someone to get into the endzone from the goal line? Johnson can do it. Need a player besides Andre Ellington who can catch screens and get yards? Johnson can do it. Need a balanced return man? You get the point.

Some of Arizona’s rookies are at positions that the Cardinals have a lot of set players. Johnson, however, plays a role that the Cardinals desperately need. Much has been made of his potential to bring life back into the running game in Arizona. If he gets chances to do that, he’ll be able to do several things to help the Cardinals become a better football team.