When quarterback Joe Flacco lines up in the Ravens' backfield this fall, he'll be protected by four of the five offensive linemen who started in the Super Bowl. Flacco threw three touchdown passes with no interceptions and was named the Most Valuable Player following the Ravens' victory over the San Francisco 49ers, taking advantage of the protection provided by his line. With the Ravens retaining left offensive tackle Bryant McKinnie on a two-year deal worth up to $7 million, Flacco is excited about the continuity along the line. The only starter who's not returning is six-time Pro Bowl center Matt Birk, who retired this offseason, with Gino Gradkowski the front-runner to take over center in a competition with A.Q. Shipley.