One of the main reasons that Matt Birk was so valuable to the Ravens as his age slowly ticked toward 40 is that he had a high football IQ that served as a big benefit to a young, developing quarterback in Joe Flacco.

Yes, Birk went to Harvard, as we were reminded constantly by TV play-by-play guys who couldn’t come up with anything more insightful to share. But the Ravens say intelligence is an attribute both Gino Gradkowski and A.Q. Shipley, the two contenders to replace Birk, share even though they didn’t go to Ivy League schools.

“They're very smart centers. They've all gotten us in the right protection. They've gotten the run calls made correctly,” Ravens head coach John Harbaugh said a couple of days ago. “So it's going to be a great battle."

As offensive coordinator Jim Caldwell put it Thursday evening, the center “is like the quarterback in the line.” Crouching over the line of scrimmage seconds after slamming helmets with a 300-pound defensive tackle, the center must identify the MIKE linebacker so he can establish blocking assignments, call out those assignments in a loud stadium filled with rowdy fans, and alert his fellow linemen if the quarterback audibles or makes a change to the play called in the huddle. The center can suggest changes, too, but Flacco has veto power.

In some systems, the quarterback might handle the blocking assignments, but Shipley, who learned from run game coordinator Juan Castillo when both were in Philadelphia, said it is Castillo’s preference that the center make those calls.

“He’s real big on letting centers call things,” Shipley said. “And Joe and I kind of do some things when I’m in there with him. He might override me or I might say something. Communication is huge.”

That’s why when I asked Caldwell what was the most essential quality he needs in a center, he said intelligence without hesitation.

“We really need to know what’s going on and where we’re going and make sure everybody is on the same page,” Gradkowski said. “Because if we’re not, it could be disastrous.”

Especially for the quarterback’s rib cage.

Of course, Flacco is no longer a young, developing quarterback. He is in his sixth season, and the tables have turned. Now he is the one who is helping two inexperienced centers find their way.

“Joe has been around and knows the system, so he can help a lot in that regard,” Caldwell said. “But nevertheless, that part of it -- the mental part of the game for a center -- is difficult.”