SANTA CLARA, Calif. -- After a rookie season in which he mostly avoided off-field issues, San Francisco 49ers linebacker Reuben Foster was arrested twice within the first month of the offseason.

The first of those arrests came on Jan. 12 in Tuscaloosa, Alabama, on suspicion of second-degree marijuana possession, a misdemeanor. The second, a more serious situation, came on Feb. 11 in nearby Los Gatos with charges of alleged domestic violence, threats and possession of an assault weapon. Neither case has reached a resolution, as Foster's hearing for the marijuana arrest was recently pushed back to next month and the Santa Clara County district attorney is still determining whether to pursue formal charges for domestic violence, threats and possession of an assault weapon. That investigation is ongoing.

Those incidents have left coach Kyle Shanahan wondering, like many, whether Foster can stay out of trouble and enjoy a long and successful NFL career.

"Yeah, anytime you’ve gotten in trouble, whether -- and again, we are talking about a case so I don’t know if anything is going to happen or not -- but any time that stuff does come out, you’re subject to be suspended from the league," Shanahan told Bay Area reporters at the scouting combine on Thursday. "So anytime that starts happening, regardless of what they decide, that’s always a risk. We’re very well aware of that and we have to take that into account. He has put us in a tough situation. Hopefully, it works out for all sides. But that is realistic. If I said it wasn’t, that wouldn’t be very smart of me."

Shanahan and general manager John Lynch have addressed Foster's situation publicly this week for the first time. Because the investigation is ongoing, neither offered much detail on where Foster stands.

Even if Foster avoids punishment for his legal issues, he will still come under the scrutiny of the NFL's policies on both substance abuse and personal conduct, which could result in a lengthy suspension.

After the Niners traded up to draft him No. 31 overall last year, Foster entered the league with questions about his ability to stay out of trouble. He failed a drug test at last year’s scouting combine because of a diluted sample and was sent home early from that event for arguing with a hospital worker.

While the 49ers don't yet know what form Foster's future will take, they do know this much: They have to begin putting in contingency plans for the possibility that Foster won't be available for all 16 games.

“That would be something that we have to take into account, whether it be in free agency or not, whether it be re-signing our own guys or whether it be in the draft,” Lynch told reporters. “That’s certainly something we’re aware of and are taking into account.”

Before Foster's issues arose, one could have made a sound argument that the Niners needed to bolster their depth at linebacker. The plan moving forward was to have Foster take over as the middle linebacker with veteran Malcolm Smith returning from a pectoral injury to step in as the starter on the weak side. Beyond that, the 49ers figured to bring back youngsters Mark Nzeocha and Elijah Lee and hoped to re-sign veteran Brock Coyle, who likely will return but is recovering from a shoulder injury.

Now, Foster's uncertain status could well make adding a capable starter at linebacker more of a priority. In fact, a variety of mock drafts already have popped up connecting the Niners to players like Georgia's Roquan Smith and Virginia Tech's Tremaine Edmunds with their first-round pick. Another, perhaps more realistic, scenario would have San Francisco finding a dependable veteran in free agency to provide some depth and drafting another in the middle rounds.

Regardless of the level, there's little question the 49ers must make at least some sort of semi-substantial investment in the position.

"Reuben was great for us when he was around, and things have happened since he’s been gone and these are things we have to address and things we need to make sure that he learns how to do things the right way," Shanahan said. "I want to help Reuben out just like I want to help any of our players out, but it’s a two-way street."