49ers' 2015 season falling apart after another young player retires

Jim Tomsula must feel like he has the cooties.

The San Francisco 49ers team that Tomsula is inheriting as its new head coach suffered another major loss Friday when right tackle Anthony Davis announced he wouldn't be playing in 2015.

"After a few years of thought, I've decided it will be best for me to take a year or so away from the NFL," Davis said in a statement. "This will be a time for me to allow my brain and body a chance to heal ... I'm simply doing what's best for my body as well as my mental health at this time in my life."

The 25-year-old Davis, who was addled by concussions as well as leg and shoulder injuries the past two seasons, later added on Twitter that he will "be back in a year or so."

By then, the 49ers could have the No. 1 overall pick in the 2016 NFL Draft if this disastrous offseason is a sign of what's to come when the games begin.

Davis joins defensive end Justin Smith and linebackers Patrick Willis and Chris Borland as the fourth 49ers player to retire this offseason citing medical concerns. The exodus doesn't stop there. Running back Frank Gore -- who, like Smith on defense, was the heart and soul of San Francisco's offense -- is now with Indianapolis. Seven other notable veterans left via free agency as well.

Replacing all the talent that signed deals elsewhere will be hard enough, especially with 49ers general manager Trent Baalke not hitting home runs with his 2012 and 2013 draft classes. Unexpectedly losing standout players who are just entering their prime like Davis and Borland is a killer.

That trickles down upon Tomsula, who was already facing the daunting task of trying to fill Jim Harbaugh's shoes after he was run out of town by 49ers brass.

If there's one division where you can't afford a shoddy offensive line, the NFC West is it. St. Louis has the NFL's most talented and deepest defensive line. Seattle and Arizona excel in bringing the heat with their pass rush.

The Cardinals raided one of San Francisco's top offensive linemen earlier this offseason when signing left guard Mike Iupati to a five-year, $40 million contract. The early frontrunner to replace Iupati is Brandon Thomas, who spent all of his rookie season on injured reserve recovering from a knee injury. Career backup Joe Looney is a fallback option.

San Francisco's right tackle spot is just as shaky. Erik Pears, a 32-year-old journeyman now on his fifth NFL team, and 2015 seventh-round pick Trent Brown are the most likely fill-ins for Davis. The 49ers could also move Alex Boone to right tackle, but that would then create a hole at right guard.

These problems could make Colin Kaepernick more of a running quarterback once again this season for the wrong reasons.

Combined with the uncertainty of Tomsula's prowess as a head coach, the 49ers have the makings of a last-place NFC West team. Free-agent signings like Darnell Dockett, Torrey Smith and Reggie Bush should be wondering what mess they've gotten themselves into.

But as bad as this sounds, there is a silver lining for Tomsula. He now has a built-in excuse for failure in Year 1 with his roster having become a train wreck.