Alan Diaz/Associated Press

There's no such thing as a franchise running back these days, but at the running back position, there's no such thing as too much of a good thing.

Instead of running one guy into the ground, NFL teams are trying to spread the love across a number of backs on their depth chart. The Miami Dolphins have been searching for a multiheaded monster in their backfield for years, but have failed to do so for several reasons, be it injuries or poor personnel decisions.

This year, though, it appears the Dolphins may finally have their answer. Between Lamar Miller and Jay Ajayi, the Dolphins have two backs who should provide an effective rushing attack in 2015. Miller was the bell cow for the Dolphins offense last year—regardless of any distinction as a "franchise running back"—but Ajayi has a chance to emerge as the Dolphins' No. 1 back by the time the season is over.

There are few, if any, backs left in the NFL who can truly call themselves franchise running backs. That's because few backs can do everything: from running between the tackles to breaking off long gains in space to catching passes out of the backfield to blocking in the backfield in pass protection and everything in between.

Aside from skill set, teams just aren't putting that kind of workload on the shoulders of one back these days. In 2014, there were only 17 running backs in the NFL who notched 200 carries or more on the season. That was down by five from 2013, and was the fewest since 1993.

Ajayi has the skills to carry out all of the aforementioned responsibilities—whether it will result in him getting 200 or more carries next season is another story.

The fact is Ajayi can be much more than a one-dimensional back, and can find his way onto the field in a number of situations. 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 finished the 2014 season with 347 carries and 50 receptions at Boise State.

Make no mistake; Ajayi is far from a finished product, and he'll have to work on ball security (11 fumbles over his last 600 carries) if he's going to be trusted as a go-to running back. That being said, he already possesses a well-rounded skill set.

2014 draft prospects, yards per route run (top 5) Player Team Targets Rec yards Snaps in route YPRR Javorius Allen USC 52 463 270 1.71 Duke Johnson MIA 56 421 249 1.69 Mike Davis SC 41 368 221 1.67 Bradley Miller TST 60 431 275 1.57 Jay Ajayi BSU 56 535 346 1.55 Source: Pro Football Focus

"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.

The Dolphins' 2012 fourth-round selection is entering the final year of his rookie deal in 2015, meaning the Dolphins must make a decision on whether or not they want to keep him around beyond this season. If Ajayi can prove that he would make a solid insurance policy against Miller's departure, he would also give the Dolphins more leverage at the negotiating table.

That's especially true if Ajayi can prove that he can do everything Miller can do, and then some.

The initial reaction to the selection of Ajayi was that he could be a solid between-the-tackles back to complement Miller. However, the Dolphins don't necessarily lack faith in Miller's ability to do the dirty work in short-yardage situations.

"I don't have the stats in front of me," head coach Joe Philbin said, "but I know I've looked at them and they're not as bad as you would think. I can think of a couple goal-line touchdown runs that he's had. One in Chicago, one in New England I think he had. Green Bay I believe he scored in a red-zone, goal-line type situation. Those are just popping into me. I thought he played well."

In 3rd-and-1 or 3rd-and-2 situations last season, Miller had 14 carries for 68 yards (4.9 yards per carry) and two touchdowns, and 11 of those carries turned into either a first down or a touchdown. Miller also had 27 carries from the 10-yard line or closer, picking up 60 yards (2.2 yards per carry) and seven touchdowns on those carries.

Even with those stats, and even with more mass on his frame (5'10", 224 pounds), it would be a stretch to say that physicality has become Miller's calling card in the way it's been Ajayi's. That's not all. What Miller hasn't done well, where Ajayi excels, is pass protection. Zierlein remarked in his scouting report that while Ajayi "shows good blitz recognition," his "pass-protection technique needs some improvement."

Ajayi might walk up to Miller at some point during camp singing this little ditty. Ajayi's abilities, plus Miller's uncertain contractual future with the team, could add up to more opportunities for the rookie than the veteran. The only thing that needs to happen is that Ajayi must make it through the season healthy.

Considering his checkered medical record, that could be easier said than done. Ajayi is four years removed from an ACL tear that did so much damage it resulted in bone-on-bone, with damage to the surrounding cartilage. He could be the next big thing or the next big bust. That spectrum of possibility is probably what led to his draft-day slide.

The good news is Ajayi made it through spring practices without a scratch, and did so without any protection on his knee.

"I felt great," Ajayi said, via Adam Beasley of the Miami Herald. "I felt healthy. I felt great. I'm happy to be out here. This is a dream come true for me, and I’m just out here trying to perform."

Prior to the 2015 NFL draft, the Dolphins depth chart at running back was loaded with players sharing a skill set of quickness and speed in the open field, but all leaving something to be desired between the tackles.

Miller has shown some ability in that area, but if Ajayi can show the Dolphins that he can take the beating between the tackles and also provide a spark in the passing game, it might only be a matter of time before he's the lead back on the Dolphins depth chart.