Ravens coach John Harbaugh dismissed Birk's absence Monday, saying the 15-year veteran was simply taking advantage of Harbaugh's tradition of giving players age 30 or older the opportunity to take a day off.
"Matt's at a stage in his career where he's going to practice less than he's not going to practice," Harbaugh said of Birk, who turned 36 last week. "And I think that would be the best thing for Matt getting ready to go."
Still, it's difficult to overlook Birk's history of health concerns. Neck, elbow and knee injuries have hampered him in his first three seasons with the Ravens, and he re-signed with the team this offseason despite reports that he was contemplating retirement. He also missed June's mandatory minicamp after undergoing surgery to repair varicose veins in his legs.
With Birk sidelined, rookie center Gino Gradkowski has taken snaps with the first team the past two days. He is widely considered the franchise's center of the future, but could be asked to assume a larger role than anticipated this season should Birk, who hasn't missed a start since 2005, be knocked out of the lineup.
"He's learning technique," Harbaugh said of Gradkowski. "He's a young guy physically. He's very smart, he's very tough and he's very competitive and kind of just a tough guy. So we like his style."