What Are Reasonable Rookie Expectations for Miami Dolphins RB Jay Ajayi?

Productive running backs can be found in all shapes, sizes and rounds of the NFL draft. The Miami Dolphins tested that theory with the selection of Boise State's Jay Ajayi in the fifth round. 

As a rookie, the expectations for Ajayi will hinge on what the Dolphins choose to do with incumbent bell cow Lamar Miller. The Dolphins drafted Miller in the fourth round in 2012, and the former Miami Hurricane got his first taste of full-time action in 2014 due in part to injuries at his position.

Now, the Dolphins appear to be gearing up to move on from Miller after the 2015 season; his contract is set to expire in March 2016, and the Dolphins may want to invest their money elsewhere. After all, over the years, we've seen plenty of examples of a lack of consideration for the running game from the Dolphins' coaching staff. 

Under head coach Joe Philbin, the Dolphins have run the ball 20 or fewer times in 17 games, third-most in the NFL in that time. So, what does all of this mean for Ajayi's production as a rookie?

Player	Car	Yds	YPA	TD	Rec	Yds	YPR	TD	Fum
Stepfan Taylor	36	115	3.2	0	8	71	8.9	0	0
Joseph Randle	54	164	3.0	2	8	61	7.6	0	0
Chris Thompson	3	12	4.0	0	6	27	4.5	1	0
Zac Stacy	250	973	3.9	7	26	141	5.4	1	1
Mike Gillislee	6	21	3.5	0	0	0	0	0	0
Chris Rainey	26	102	3.9	2	14	60	4.3	0	4
Vick Ballard	211	814	3.9	2	17	152	8.9	1	3
Johnny White	12	38	3.2	0	1	-3	-3	0	0
Jacquizz Rodgers	57	205	3.6	1	21	188	9	1	1
Dion Lewis	23	102	4.4	1	1	-3	-3	0	1

Thanks to a little research, we were able to compile a list of all running backs drafted in the fifth round from 2011 to 2014, complete with how they performed as rookies. 

On average, these backs have carried the ball 67.8 times for 254.6 yards (3.8 yards per carry) and 1.5 touchdowns, with 10.2 receptions for 69.4 yards (6.8 yards per reception) with 0.4 touchdowns. 

The range of production is all over the map. With Miller in the fold, the Dolphins probably will not be asking Ajayi to carry the load like St. Louis Rams running back Zac Stacy or Indianapolis Colts running back Vick Ballard, each of whom finished their rookie season with more than 200 carries. 

That being said, considering the possibility that the Dolphins will look to phase Miller out and Ajayi into their offense, it seems like a lowball estimate to say the Dolphins rookie will finish with fewer than 50 carries and 200 yards, as most of the other backs did. 

It's more likely that the truth is somewhere in between. 

The Dolphins do not need Ajayi to be more than a complementary back in his first season. Considering the Dolphins' ignorance of the running game in the past, there may not even be enough carries to go around for Ajayi to be more than a rotational piece in the offense.

There are concerns about the durability of Ajayi's knee, but according to Adam Caplan of ESPN, there are no short-term concerns about whether he can hold up or be ready for the 2015 season. Therefore, there should be no concerns over whether his knee will inhibit his production as a rookie.

Miller's rookie season can be seen as a barometer for Ajayi's, but Ajayi is a much different back than Miller—which is part of the reason why the Dolphins brought him in. Not only is Ajayi capable on all three downs, he also has a reputation as a hard between-the-tackles runner.

That being said, Ajayi may not immediately threaten Miller for the No. 1 role in the Dolphins offense. According to Omar Kelly of the South Florida Sun-Sentinel, Ajayi is more likely to challenge for the third-down role than the first- and second-down role. 

Besides, not only is Miller much more experienced in the NFL, but he's also in a contract year. That means the Dolphins can squeeze every last ounce of juice out of him before casting him off to the free-agent market. 

Given Ajayi's ability to fill a vacant niche in the Dolphins offense, it would be a surprise if Ajayi finishes with fewer than 70 carries, 300 yards and three touchdowns. He could be even more effective on passing downs, though, so expect him to earn at least 30 receptions, 200 yards and a touchdown as a receiver. 

Unless otherwise noted, all advanced stats obtained via Pro Football Focus.