How big a fantasy impact can Arian Foster have in Miami?

— -- The Miami Dolphins spent the offseason pursuing running back depth, and on Monday they found it, signing veteran Arian Foster to a one-year, $1.5 million contract.

Among those pursuits:

- The Dolphins unsuccessfully attempted to re-sign Lamar Miller.

- They agreed to an offer sheet with C.J. Anderson that was matched by the Denver Broncos.

- They were rumored to be considering trading up in the NFL draft to make a run at Ezekiel Elliott.

All three are starting-caliber talents, which is why Foster's arrival in Miami isn't good news for Jay Ajayi, who for four months appeared a potential breakout candidate as the team's starter. It gives an impression that new head coach Adam Gase never truly trusted Ajayi with a potential bell-cow role.

During that time, Foster also had 20 games that ranked among the top 25 weekly scores at his position, and only two that fell outside the top 50.

Unfortunately, Foster also missed 23 of 48 total team games during that time, and he'll begin the 2016 season at the age of 30, coming off a ruptured Achilles' that resulted in his March release by the Texans. It is a significant injury from which to recover for any running back, but especially so for a player of Foster's age. To assume that he'll be 100 percent by Week 1 remains a bit of a stretch.

This thrusts Foster into the risk/reward bin, and fantasy owners' immediate reaction might therefore be that of frustration, watching another backfield slip into a potential timeshare. Though that's true -- Ajayi's fantasy value suffers significantly, while Foster has too many durability questions to be fully trusted -- this could actually make either player a value opportunity in leagues that have yet to draft.

Foster, after all, likely chose this spot under the impression that he'd get a chance to prove to Gase that he's capable of handling starter's duties once healthy. With a promising preseason, Foster could move to the lead of this backfield within the first few weeks of the regular season, or at the very least be a significant contributor in the receiving game.

In PPR leagues, a healthy Foster -- to be clear, one with positive, near-glowing August reports -- could slip beneath the radar, and even in standard leagues he'd be involved enough to warrant consideration in the sub-flex-play tier, the range from which fantasy owners typically build roster depth at the position to mix and match around matchups. If there's one thing we've known about Foster through the years, it's that he's a definite fantasy start in the games he's an NFL starter. It's investing in the long term that is the risky business with him.

Ajayi, meanwhile, would remain one of the wisest backups to stash in the later rounds, under the guise that Foster will miss time in 2016 (and he almost certainly will, considering his injury history). Even a 10-spot drop in the running back rankings would make him well worth the speculative pick for a potential RB2 contribution later in the season during one of Foster's absences.

Previously my No. 22 running back, Ajayi dropped to 30th in my rankings as a result of Foster's arrival, while Foster, originally No. 48 as a free agent, moved up to 39th.