(UPDATE: Birk officially announced his retirement Friday morning. Here's the full story.)
Ravens six-time Pro Bowl center Matt Birk will announce his retirement from the NFL later this morning, according to a source with knowledge of his plans.
Birk, 36, played in the NFL for 15 seasons and won a Super Bowl in his final season with a victory in Super Bowl XLVII over the San Francisco 49ers in New Orleans.
Birk played well last season and could have continued to play, but the Harvard graduate, former Walter Payton NFL Man of the Year and married father of six opted to leave the game at this time.
Birk is set to meet with students at Battle Grove Elementary School in Baltimore later today at 11:30 a.m. to dedicate a community reading center, the team announced, saying he also planned on "making another announcement," during the ceremony.
Birk had two years remaining on his three-year, $8.525 million contract with base salaries of $2.75 million in 2013 and 2014. The contract included a $2.1 million signing bonus.
With Birk's retirement, the Ravens will realize a savings credit of $2.05 million against the 2013 salary cap. That would place them at $12.864 million under a projected salary cap limit of $122 million with another $4.35 million to be gained when middle linebacker Ray Lewis officially retires.
Birk was regarded as one of the Ravens' most community-oriented players and one of the Super Bowl champions' most cooperative players with the media.