BALTIMORE - A big hole could soon be left in the Ravens roster. Center Matt Birk could be announcing his retirement on Friday.
Birk is expected to make an announcement during a school appearance on Friday. ESPN.com reports that announcement is he is retiring.
Birk spent the first 11 seasons of his career with the Minnesota Vikings before signing with the Ravens in 2009.
He is a 1998 graduate of Harvard and won the NFL's Walter Payton Man of the Year award in 2011.
The 36-year-old has been voted to the Probowl six times.
Birk announced earlier this month he'll eventually donate his brain to Boston University's School of Medicine for research into concussions.
His event is at an elementary school in the city at 11:30 a.m.