Miami Dolphins: Full Position Breakdown and Depth Chart Analysis at Running Back

If the Miami Dolphins field an efficient offense in 2015, it will not necessarily be because quarterback Ryan Tannehill was the glue that held them together.

Offensive coordinator Bill Lazor may seem to have a preference for the passing game, as evidenced by his team's 641 pass plays (61.6 percent) and 399 running plays (38.4 percent), but consider the league-wide disparity between the run and the pass (58.2 percent pass, 41.8 percent run) and the Dolphins suddenly look a little more balanced than it would appear on paper.

Also consider that the Dolphins averaged 4.7 yards per rush attempt in 2014, seventh-highest in the NFL, and it becomes a little clearer that they should continue to keep a balanced approach—maybe even skew the numbers a little more toward the running game to take advantage of their effectiveness in that area.

Last year, veteran running back Lamar Miller fell into a role as the bell cow for the offense due to an injury suffered by Knowshon Moreno. It looked as though Miller would enter the 2015 season as the lead back, but with the fifth-round selection of Boise State's Jay Ajayi, the Dolphins appear to be open to the idea of a rotation in the backfield, or possibly even a competition for the top spot.

Here's an in-depth look at the entire depth chart as it stands.

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Lamar Miller

The Dolphins drafted Lamar Miller in the fourth round of the 2012 draft at a time when Daniel Thomas was the No. 2 back and Reggie Bush was entering what would be his final year with the Teal and Orange.

Two years later, Miller emerged as the No. 1 back in the offense by attrition; Knowhon Moreno's lone season in Miami turned out to be an injury-plagued one, and the Dolphins turned to Miller to be the top option in the rushing attack.

Their confidence was rewarded with a 1,000-yard season—the first by a Dolphins back since Bush in 2011—but Miller's success was not based solely on volume. He also averaged 5.1 yards per carry, the most by a Dolphins back since Ronnie Brown in 2007. Miller added 38 receptions for 275 yards and a touchdown, proving that he can also be an effective option in the receiving game.

He will need to improve in pass protection, where he has struggled throughout his career, and he will also be competing with Jay Ajayi for carries. But that's not all he'll be competing for.

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Jay Ajayi

Entering the 2015 NFL draft, the Dolphins had a depth chart loaded with running backs that shared a skill set of dominance on passing downs, all of whom left a little something to be desired in terms of their between-the-tackles running ability. Yes, Miller displayed some hard running in his breakout 2014 campaign, but the Dolphins still needed a proven, physical back.

Jay Ajayi offers that and so much more. In fact, according to Lance Zierlein of NFL.com, while physicality "has become [Ajayi's] calling card," he is a "true weapon out of backfield with adequate hands and good feel for maximizing each catch in space." He had 347 carries and 50 receptions in 2014. 

There are areas Ajayi needs to improve, such as ball security (11 fumbles over his last 600 carries), but he's also one of the more well-rounded backs the Dolphins could have found in this year's draft class. 

"Of all the backs in this draft, Ajayi might be my favorite because he can do everything you want from a back and you don't have to find a complementary back to pick up the slack for him in any one area," said one AFC scout, according to Zierlein. 

If the scouting report proves to be true, Miller's days in Miami could be numbered.

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Damien Williams

Damien Williams found his way into a nice niche with the Dolphins as a backup scatback, reeling in 21 passes for 187 yards and a touchdown in 2014. His role was much bigger on passing downs (111 total snaps) than on running downs (51 snaps), according to Pro Football Focus, and it figures to remain that way in 2014—and that's assuming Ajayi doesn't soak up even more snaps.

Williams may need to contribute in other areas, such as in the running game, where he notched 36 carries for 122 yards, or in the return game, where he had five kickoff returns for 102 yards.

For now, he is living up to his predraft billing as a back who is "best running outside in a spread offense that features wide running lanes and could bring the most value to a team as a pass catcher in a change-of-pace role," as described by NFL.com's Nolan Nawrocki. He may need to pick up the slack in other areas in the immediate future if he wants to stick around to get opportunities to expand his role.

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LaMichael James

Notwithstanding his skill set, which is awfully similar to at least two other backs on the Dolphins roster, LaMichael James isn't likely to make much of an impact in the running game. He's not likely to make much of an impact in the receiving game, either. 

The return game is James' best bet for making his presence felt. He didn't get any opportunities to return kicks for the Dolphins in 2014, but he was used primarily on special teams with the San Francisco 49ers. In 2012 and 2013, James had 26 kickoff returns for 738 yards (28.4 yards-per-return average) and 23 punt returns for 251 yards (10.9 yards-per-return average). 

If given an opportunity to prove himself on special teams, James could still fight for a roster spot. That being said, the return duties were held down primarily by 2014 rookie wide receiver Jarvis Landry. The Dolphins may not want Landry on returns again this year, since he'll continue to be a very important piece on offense, and if James can prove he's still effective in that role, he could be the one to take on the responsibility. 

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Mike Gillislee

It appears Mike Gillislee is on the outside looking in on the competition for playing time in the Dolphins backfield. 

Not only is Gillislee redundant from a skill-set standpoint, but he just hasn't had many opportunities to prove he can make the transition from college to the pros. 

Gillislee was drafted in the fifth round in 2013, but has earned only six carries in his two-year career. It doesn't appear he's moving up the depth chart at all, either; according to Barry Jackson of the Miami Herald, Gillislee has been working as a fifth option in the rotation at the Dolphins' organized team activities. 

Jackson even reported, less than a year after the Dolphins drafted him, that the team wasn't sure "when or if [Gillislee] will become more than a third-stringer." At this rate, Gillislee could be packing his bags in just a few short months. 

Unless otherwise noted, all advanced statistics provided by ProFootballFocus.com.