The Miami Dolphins allowed Lamar Miller to walk in free agency and struck out on C.J. Anderson (who returned to the Denver Broncos after they matched Miami's four-year, $19 million offer sheet) and Chris Johnson on the open market. That leaves 2015 fifth-rounder Jay Ajayi as the only running back of note on the Dolphins' depth chart. Yes, in case you're wondering, that is a cause for concern.

So much so, in fact, that the Dolphins are doing everything they can to plug the growing hole. Other free agent backs such as Arian Foster, Ronnie Hillman, Joique Bell and Reggie Bush don't seem to be of much interest to Miami as of now, so the Dolphins are exploring other avenues.

Miami is reportedly entertaining the possibility of acquiring a starting running back via trade. While no deals are imminent, the organization has reportedly sent out feelers to "multiple teams" to gauge potential interest.

Miller walked away from the Dolphins to the tune of $6.5 million per season from the Houston Texans. The Dolphins then had a keen eye for Anderson, but he chose to return to the reigning Super Bowl winners. Johnson took a visit with the Dolphins but ultimately re-upped with the Arizona Cardinals on a one-year deal worth up to $3 million. That is why Miami is now exploring possible trade options, while a veteran free agent or young draft pick remain possibilities as well.

None of this reflects well on Ajayi, who carried the ball 49 times for 187 yards (3.8 YPC) and one touchdown in nine games last year. However, new Dolphins head coach Adam Gase says Miami's interest in RBs has nothing to do with Ajayi's performance last year.

"The reason we were trying to do that is we're looking to having more than one guy," Gase said. "Jay is going to be a big part of what we're doing. I'd like to have multiple backs. Right now, we don't have a lot of guys on the roster. I think we only have three guys on the roster right now. We're going to need to really develop that stable of backs.

"Options will present themselves. We just need to stay patient, whether it's through the draft or somebody gets cut free or there's somebody else out there that we need to take a look at. We'll just keep investigating that. I guess for me, I feel really comfortable with Jay. I saw a lot of good things on film last year. I'm fired up to get going with him. The problem is, we can't do anything until April 11th. But really, those two weeks are meetings and weightlifting. Really, that minicamp will be our first good look t to see where we're at with our running backs."

Follow Brandon Katz on Twitter at @Great_Katzby