SANTA CLARA, Calif. -- The San Francisco 49ers quite possibly gained a starting right tackle on Saturday afternoon, when the NFL reinstated Anthony Davis after his yearlong hiatus from football. But Davis' addition had to come with a subtraction, and in this case, that subtraction wasn't simply a camp body sitting at the end of the roster.

To make room for Davis, the 49ers placed starting nose tackle Ian Williams on the reserve/non-football injury list because of an ankle issue that required offseason surgery. In simpler terms, Williams' 2016 season is over before it began.

Although Davis can certainly help fill a void on a 49ers line that ranked 31st in the NFL in pass protection rate in 2015, according to ESPN Stats & Info, losing Williams is a significant blow to San Francisco's defense, particularly against the run.

Williams has struggled with ankle issues in the past and missed parts of the 2013 and 2014 seasons with similar ailments. He took to Twitter on Friday night to say that a comeback isn't out of the question this time, either.

I've done it before and I'll do it again...

— Ian Williams (@IWilliams95) July 30, 2016

The 49ers hoped to have Williams as the centerpiece of their base 3-4 defense before he suffered the ankle injury. The team and Williams reportedly agreed to a five-year deal worth $25-30 million in the offseason, but the ankle issue ultimately prevented that deal from getting signed.

Instead, Williams inked a one-year deal worth $1 million plus incentives. Now that he's out for the season, he will be unable to earn those incentives, and the Niners' defense will have to replace an important and underrated cog.

Williams, who worked his way from being an undrafted free agent out of Notre Dame in 2011 to a starter, had 65 tackles, a sack, a forced fumble and a fumble recovery in 2015. For what it's worth, Pro Football Focus rated Williams as the team's best defender last season, and his 37 run stops tied for third in the NFL. All of that came in Williams' first full season as a starter.

The Niners have some options to replace Williams, including Quinton Dial, who handled the job in 2014. Assuming he can get back to full strength, Glenn Dorsey, who is still recovering from a knee injury suffered in November, could slide back into the role he played in 2013. Mike Purcell, Garrison Smith and undrafted rookie Darren Lake are other potential options.

As for Davis, this training camp will be essential for him to prove that he is not only in shape but also committed to playing again after he took last season off. Davis surprised the football world by announcing his "retirement" last June after he dealt with some injury problems, including a concussion, in 2014. It was long expected that Davis would return, but he didn't make it official until last week, when he applied for reinstatement.

That application was approved Saturday afternoon, and Davis now must begin the process of earning his spot back against a group that includes veterans Trent Brown and Erik Pears, as well as lesser-known commodities such as draft picks John Theus and Fahn Cooper.

Clearly, Davis has the most accomplished track record of that group, but he missed the team's spring practices. That likely means he'll have a bit of a wakeup call when he steps on the field for one of coach Chip Kelly's hyper-drive practices.

When it comes to regaining the trust of his teammates after a tumultuous year in which he didn't play and occasionally took to Twitter to air his grievances, Davis will have some work to do to re-establish himself, but he is being welcomed back.

"It’s good to have him back, definitely," running back Carlos Hyde said. "He’s a guy that’s going to be able to come in and help our offensive line out a lot. We have also got young guys who are going to be competing for that spot too, so I don’t think anything is going to be given to him. He’s definitely going to have to come in and work for it, just like everybody else has got to come in here and work for their spot, so I’m really looking forward to training camp, where you really get to see what you have."

Over the next month-and-a-half, that means a long look to see if Davis can regain his previous form and, once again, finding a replacement to fill the hole in the middle of the defensive line.