Anthony Davis retiring another blow for rebuilding 49ers

Speaking slowly and deliberately at his locker in December, Anthony Davis was frustrated and frightened.

It had been more than two weeks since the San Francisco 49ers right tackle had taken what he called a “spinning elbow” to the helmet in a game at the New York Giants, and he was still feeling the aftereffects of a concussion.

“It’s not fun,” Davis said that day. “It’s scary when your brain’s not working the way it’s supposed to. And the culture of the league is, You’re a big, tough guy.”

So suck it up, right?

Except Davis admitted to feeling loopy, which was his word, not that of the reporters surrounding his locker.

“It was like a white fog,” he added, shielding his face with a hand. “When you look out, it’s a white fog. Or just having a simple conversation [is hard]. You just feel slowed down.”

Is it any wonder, then, that Davis, at just 25 years old but after five trying seasons in the NFL, joined 49ers teammates Patrick Willis, 30, Chris Borland, 24, and Justin Smith, 35, in announcing his retirement on Friday?

Davis had not attended any of the 49ers’ voluntary OTAs this offseason and said his health was at the root of his decision.

“This will be a time for me to allow my brain and body a chance to heal,” he said in a statement.

“I'm simply doing what's best for my body as well as my mental health at this time in my life.”

The sentiment echoed the thoughts of Borland, who feared brain injury, and Willis, who said his injured feet would not allow him to play at the level to which he was accustomed. Smith, after 14 seasons, simply said he was done.

From a football perspective, Davis’ retirement is the latest blow to a team already reeling from retirements, free-agency defections and cuts.

Adding Davis, the Niners have now lost 12 players who started at least six games last season -- Borland, Willis and Smith, plus running back Frank Gore (Indianapolis Colts), left guard Mike Iupati (Arizona Cardinals), linebacker Dan Skuta (Jacksonville Jaguars), cornerbacks Chris Culliver (Washington) and Perrish Cox (Tennessee Titans), receiver Michael Crabtree (Oakland Raiders), defensive lineman Ray McDonald (cut) and offensive lineman Jonathan Martin (waived/Carolina Panthers).

In fact, it was Martin who stepped in for Davis last year at right tackle. The move did not work well for the Niners.

Remember, Davis, the No. 11 overall pick of the 2010 draft out of Rutgers, started the first 64 games of his career before shoulder, hamstring, knee and ankle injuries slowed him last season. And that was before the concussion.

He played in seven games a year ago, and the Niners’ preseason projected offensive line of LT Joe Staley, LG Iupati, C Daniel Kilore, RG Alex Boone and Davis played together for just one-plus quarter all of last season.

Davis was a key cog of the Niners’ once-vaunted power-running attack, and with him injured and out of the lineup, it suffered. Mightily.

Seventh-round draft pick Trent Brown has been running with the first-team offense at right tackle during OTAs and, while the practices are essentially glorified flag-football scrimmages, he has impressed the coaching staff.

But it was Davis, a social media maven in his own right, one who freely speaks his mind on any and all social matters, who defined the ruggedness of the Niners' offensive line.

Trent Baalke, the 49ers' general manager, thanked Davis “for his contributions to our team over the last five seasons and [wished] him the best as he moves on from the game” in a statement.

But Baalke also has insisted the Niners were not rebuilding this offseason under new coach Jim Tomsula. Rather, Baalke said, they were reloading.

Davis' becoming the third unexpected retiree in three months makes it all feel like the former.