The San Francisco 49ers had hoped Arik Armstead would only be on the sidelines a couple of weeks with knee and foot injuries. Now it's not clear if and when he will return. 

Armstead has not played since the 49ers' Week 13 win over the Philadelphia Eagles and was once again ruled out as San Francisco prepares to face the Baltimore Ravens in a massive game on Christmas Day night.

Having not practiced all week, the starting defensive tackle's status for Week 16 was no surprise. More worrying, though, were comments made by head coach Kyle Shanahan about Armstead's long-term health.

Shanahan, who confirmed Armstead is dealing with an issue similar to the plantar fasciitis that limited him to nine regular-season games last season, told his Saturday press conference: "We’re concerned, we do think he has a chance each week but it’s a little more the foot than the knee, something that’s bothered him for a little bit so just hoping the pain will go down."

Essentially, the 49ers have little idea when Armstead will be able to return, meaning they may have to get used to being without him during the final weeks of the regular season and the playoffs.

That is a worrying prospect for a 49er defense that has seen its interior pass rush brought back to life by the combination of Armstead and Javon Hargrave at defensive tackle. Hargrave is questionable to face the Ravens with a hamstring issue.

And Shanahan's remarks come at a time when the 49ers are light on depth on the interior defensive line. Javon Kinlaw has finally shaken off the injury bug and is putting together his best season of his pro career and Kevin Givens is an established part of the interior rotation. However, San Francisco this week put Kalia Davis on injured reserve with an ankle injury and have no other defensive tackles on their active roster.

The Niners added veteran Taylor Stallworth to their practice squad in the wake of Davis' injury, while T.Y. McGill was elevated from the practice squad for last week's NFC West-clinching win over the Arizona Cardinals, a game in which the Niners gave up 234 yards on the ground without Hargrave and Armstead. 

But the reality is the the 49ers don't want to be relying on practice squad players in the postseason. With Armstead's status seemingly up in the air the rest of the way, the Niners need a more viable insurance policy, meaning a move for a veteran free agent is a must. 

The 49ers last year explored signing Ndamukong Suh. They could renew that interest while they also have a chance to put a claim in for Sebastian Joseph-Day after he was waived by the Los Angeles Chargers.

With Hargrave and Kinlaw the likely starters against the Ravens, the 49ers can afford to have confidence their interior can make an impact in slowing down Lamar Jackson and Co.

But once that game is in the books, the 49ers need to find a solution that can soften the blow of Armstead dealing with what appears to be a long-term issue at the worst possible point in the regular season.

The 49ers will have to get used to being without Arik Armstead

It’s looking like a long-term issue.