49ers release LB Brock Coyle, who plans to retire from the NFL

In the same official press release, the San Francisco 49ers announced the signing of inside linebacker and special-teamer David Mayo, as well as the release of inside linebacker and special-teamer Brock Coyle.

Soon after the 49ers' official announcement, Coyle took to social media to thank the 49ers organization for re-signing him last offseason, and to explain that the neck injury he sustained in Week 1 of the 2018 regular season will force the veteran to leave the game:

San Francisco's front office was likely aware of Coyle's plans for the future. The team has stockpiled inside linebackers in recent months, culminating in Mayo's signing earlier today, which would have forced Coyle into an uphill battle for a roster spot despite the three-year, $8.5 million contract he received from the 49ers last offseason.

Although the career special-teamer had a reputation as a hard worker, Coyle became a polarizing figure for San Francisco soon after the 49ers signed him away from the Seattle Seahawks in 2017. A favorite of the coaching staff, Coyle's increased playing time in key situations forced star linebacker NaVorro Bowman first to the 49ers' bench and then to the Oakland Raiders' roster, despite the harsh cap implications of his release.

Despite playing in two new defensive systems in 2017, Bowman graded higher than Coyle in each of Pro Football Focus' five defensive grade categories, while PFF ranked Coyle as one of the NFL's worst inside linebackers. Still, Coyle was given an impressive contract offer after the conclusion of the season; unfortunately, he was able to play just a portion of one game under his new deal.

Coyle played the game of football with fire, and gave his all whenever he set foot on the field. The linebacker was a leader in the locker room and on the field of play, and will be missed by his teammates and the 49ers' organization.

Here's what the team's official press release had to say about the San Francisco 49ers' former starting inside linebacker:

"Brock contributed greatly to the culture we have been building over the last two years, and we are very thankful to have benefitted from his presence," said 49ers General Manager John Lynch. "Through his play, his character and his professionalism, he set a wonderful example of what this organization looks for in a 49er. We expect great things from Brock in whatever he chooses to do in life and wish him continued success."

Coyle (6-1, 245) appeared in 17 games (11 starts) over the past two seasons with the team after originally signing as a free agent on March 10, 2017. He registered 68 tackles, one pass defensed, one forced fumble and 0.5 sack to go along with two tackles on special teams.