Which RBs will stick with Dolphins?

DAVIE, Fla. -- The Miami Dolphins have a problem at running back. But if you poll Miami's coaching staff, most would say it's a good problem to have.

Based on their performance in training camp and the preseason, the Dolphins may have too many solid running backs to choose from. So much is the case that backup tailback and primary kick returner Marcus Thigpen is already switching positions to become a slot receiver. There simply aren't enough carries to go around.

The top four players at tailback for the Dolphins are Lamar Miller -- Miami's probable starter -- and backups Daniel Thomas, Jonas Gray and rookie Mike Gillislee. All have shown flashes and caught the eye of their coaching staff.

Typically, most teams keep three tailbacks, which could set up an interesting numbers game when it’s time to trim down to a 53-man roster.

“Yeah, I would say it’s pretty close, the running back competition,” Dolphins offensive coordinator Mike Sherman said this week. “I thought that Daniel Thomas did a really nice job in the game the other day. Certainly Miller has had his shining moments as well, and some of the younger guys have stepped up.

“So some of the finer points are going to come up. How well do you catch? How well do you pass block? I think from a running standpoint we have some pretty good runners, but to be the complete back, they have to be able to do all of those things.”

Sherman brought up an interesting point that Miami is searching for a complete running back. Miami’s top four tailbacks all have their strengths and weaknesses.

Miller is by far the best pure runner. His speed, quickness and ability to dart through defenses helped Miller lead the Dolphins last year with 4.9 yards per carry. Miller is most likely Miami's Week 1 starter, barring injury.

The Dolphins' backups have a lot to prove. Thomas is a former 2011 second-round pick who hasn’t panned out. This is a big training camp for him after a slow and injury-plagued 2012 season. Thomas must prove that he can fit in head coach Joe Philbin’s offensive system.

“I’m very happy with the way he is practicing,” Philbin said of Thomas. “I like what he is doing. I was watching him just today in special [teams]. He’s going about his business in a very professional manner.”

Miami’s two younger backs -- Gillislee and Gray -- are inexperienced but have shown eagerness to make an immediate impact. Gillislee, a rookie fifth-round pick, has run well in training camp, and Gray has done well in both exhibition games. Gray recorded 76 total yards from scrimmage in the Hall of Fame Game against the Dallas Cowboys and led the Dolphins with two touchdown runs in last week’s 27-3 victory over the Jacksonville Jaguars.

If both young players continue to do well for the Dolphins, that could make keeping only three tailbacks a tough decision. Miller is the only lock at this point. But the story continues to unfold for Thomas, Gillislee and Gray with three preseason games remaining.

Could the Dolphins really keep four running backs?

“There’s a possibility that could happen,” Sherman admitted. “I tell those guys all the time that they have to be a factor on special teams to have a role as a fourth or third running back. So really that decision, if they’re in the mix, that decision will come down to special teams, so they better make sure that they’re picking up our special-teams coach in the morning, and driving him home at night and getting him breakfast.”