Anthony Davis has retired at 25. (Getty Images)

San Francisco 49ers offensive tackle Anthony Davis announced his retirement on Friday, according to a report from NFL.com's Ian Rapaport.

Davis, 25, is the third high-profile 49er to retire this offseason.

Linebacker Chris Borland, himself just 24 years old, stunned the NFL world back in March by announcing his retirement after just one season -- a season in which he was one of the NFL's best linebackers while he was on the field.

Borland stated that he was retiring due to long-term health concerns, noting, "I just thought to myself, 'What am I doing? Is this how I'm going to live my adult life, banging my head, especially with what I've learned and knew about the dangers?'" He told ESPN's Outside the Lines, "From what I've researched and what I've experienced, I don't think it's worth the risk."

In late May, defensive lineman Justin Smith announced his retirement as well. Smith played 14 years in the NFL, seven apiece with the 49ers and Cincinnati Bengals. "Tough. Physical. Durable. Hard-working. Dedicated. Selfless. Justin embodies each of those qualities and brought even more with him to work each and every day," 49ers CEO Jed York said via the team website upon Smith's retirement. "Whether it was chasing down a wide receiver and forcing a fumble to seal a win, or driving a tackle back into the quarterback's chest, he gave everything he had every play. Justin ... will always be remembered as one of the 49ers all-time greats."

Davis, Borland and Smith weren't the only former 49ers to leave the team this offseason, either. The exodus began with head coach Jim Harbaugh, who "mutually agreed to part ways" with the team after the regular season finale and later took the head coaching job at his alma mater, the University of Michigan.

Harbaugh's coordinators, Greg Roman (offense) and Vic Fangio (defense), also left the team shortly after. Roman joined Rex Ryan with the Bills while Fangio headed to the Bears to team up with John Fox.

And even that's not all. Frank Gore, who defined the 49ers' offense for the last decade, left for the Indianapolis Colts; guard Mike Iupati departed for the Arizona Cardinals; wide receiver Michael Crabtree left for the Oakland Raiders; linebacker Dan Skuta signed with the Jacksonville Jaguars; cornerbacks Perrish Cox and Chris Culliver went to the Tennessee Titans and Washington Redskins, respectively; and backup quarterback Josh Johnson headed to the Cincinnati Bengals.

Add all that to the 10 draft picks and 10 free agent signings (including Torrey Smith, Reggie Bush and Darnell Dockett) the 49ers made, and the roster has been in a constant state of turnover throughout the offseason. The 49ers we see suit up in Week 1 will look drastically different than the team we last saw in 2014, maybe more so than any other NFL team.

UPDATE: I somehow forgot to mention the retirement of Patrick Willis, arguably the 49ers' best player ever since he was drafted with the 11th overall pick in the 2007 draft, and easily one of the NFL's best linebackers over the same time period. He played only eight NFL seasons, but he did so at a Hall of Fame level. He will be missed dearly by the 49ers' defense.