The San Francisco 49ers definitely don't have a shortage at running back heading into 2019 offseason programs.

The Niners will be getting injured returnees Jerick McKinnon and special teams ace Raheem Mostert back from 2018 ACL and forearm injuries, respectively. Third-year pro Matt Breida is poised to return after posting the fourth-best yards-per-carry average in the NFL last season (5.3). And after inking former Atlanta Falcons multifaceted standout, Tevin Coleman, in free agency, San Francisco clearly has a notable logjam heading towards training camp.

It appears to be something of a conundrum for head coach Kyle Shanahan, who discussed the problem on ESPN's Adam Schefter's podcast on April 1.

"It's up to the players," Shanahan said when prompted about the depth chart. "They will define their roles. That's kind of what's unique about this."

Coleman's two-year, $8.5 million deal all but assures he'll hold a prominent role this season. McKinnon, even though he has yet to see a regular-season snap for San Francisco, seems to be safe, too, considering how much the 49ers invested in him during the 2018 free-agent period. Mostert remains one of the league's best on special teams, so he's probably safe as well.

Breida is a slight question mark, but there's no denying his impressive efforts amid an injury-riddled 2018 campaign.

According to Shanahan, however, it's a good problem to have.

"They come in different sizes, they do different types of routes," Shanahan continued. "We played with four running backs last year so I'm not going sit here and try to think about what to do with four running backs, we might need them all.

"If they all stay healthy it will be a fun problem for us to figure out, how to utilize them as a coaching staff."

Shanahan is right about that. The 49ers running backs suffered plenty of attrition over the course of last season, and few positions take as much of a beating as running back. And considering how much Shanahan's offense relies on the ground game, keeping four on the roster for as long as possible might wind up being a smart move anyway.

Regardless, it should make for a pretty enticing and competitive training camp for these four.

h/t to NBC Sports Bay Area's Jennifer Lee Chan for the find.