The 49ers could add another running back in the offseason, all right.

They could draft a power back who provides a different style of running than the players already on their roster. Or, as many sentimental 49ers fans have suggested, they could sign veteran Frank Gore, who turns 36 in May.

But if they add a running back, somebody is going to have to sit.

The 49ers have Jerick McKinnon and Matt Breida under contract. Raheem Mostert is likely to return as a restricted free agent. As the team’s best special-teams player and a capable No. 3 running back, a healthy Mostert is assured of suiting up for every game.

The 49ers finished 13th in the NFL last season with 118.9 yards rushing per game. They tied for 12th in the league with a 4.5-yard average. Where the 49ers struggled, in particular, was near the goal line. The 49ers tied for 30th with just seven rushing touchdowns.

Yet, the 49ers were effective short-yardage situations. On third- and fourth-down attempts of 1 or 2 yards, the 49ers were successful on 21 of 26 opportunities (81 percent).

Coach Kyle Shanahan addressed his throughts on a short-yardage back a year ago after the addition of McKinnon.

“We’ll continue to look in the draft, and we’ll always look to add running backs,” Shanahan said. “When it comes to a big bruiser for the goal line, no one is just running over guys unblocked, either. You need to find open holes and be a good running back.”

 

Shanahan chose McKinnon a year ago in free agency for his running, his receiving and his ability to exploit mismatches in the middle of the field.

Make no mistake, Shanahan selected McKinnon, whom the New York Jets also pursued on the open market. The 49ers were going to go about as high as necessary to make sure they signed McKinnon.

Shanahan had big plans for a restructured 49ers offense. He envisioned an offense designed around the basic principle that defenses would be compromised when making decisions on how to simultaneously cover McKinnon, fullback Kyle Juszczyk, a healthy slot receiver, Trent Taylor, and tight end George Kittle. There would be holes in the defenses, and Shanahan envisioned Jimmy Garoppolo exploiting the weak links – especially on third downs.

But all those plans were blown up a week before the start of the regular season when McKinnon sustained a season-ending torn anterior cruciate ligament.

McKinnon continues his rehabilitation and training, and the 49ers can only hope he can return physically to somewhere close to his pre-injury form.

In McKinnon’s absence last season, Breida rushed for 814 yards despite battling knee, shoulder and ankle injuries that kept him listed as “questionable” for a large portion of the season. He averaged a hefty 5.3 yards a carry.

Mostert is scheduled for restricted free agency. The 49ers will not let him go, and could even target him for a multi-year contract extension. Mostert proved to be a valuable player on a 46-man game day roster because of his value on special teams.

And when given a chance at running back, the speedster averaged 7.7 yards a carry before sustaining a fractured forearm in Week 9 against the Raiders.

[RELATED: As expected, 49ers will not pick up option on Pierre Garçon]

Veteran Alfred Morris is not expected back, and Jeff Wilson faces an uphill climb for a roster spot despite showing some promise late in the season after his promotion from the practice squad.

So while the 49ers could easily add another running back to their mix, the bigger question is which player would be pushed aside to create opportunities for a new player.