Birk decided the offensive line should reciprocate. The problem? He'd have to do some digging to figure out what the quarterback would like.
One day, Birk casually asked Flacco, "Do you golf?"
"No, I don't golf," Flacco said.
"Do you fish?"
"No, I don't fish."
"What do you do in your off time?"
"I just like to sit around," Flacco said. "I hang out in my basement."
So what did the offensive linemen come up with?
"A pinball machine," Birk said, then took a dramatic pause. "For his basement."
Not that the image of Flacco spending his free time on a couch and with his feet up came as a complete surprise.
"He's definitely not the prima donna, pretty-boy quarterback type," Birk said. "He's just Joe."
Let's face it: These days, that's good enough. By plenty.
Flacco is 28 years old and already has six road wins in the playoffs, the most by a starting quarterback in NFL history. This postseason, he's thrown eight touchdown passes and no interceptions. He has outplayed, in succession, Andrew Luck, Peyton Manning and Tom Brady, helping the Baltimore Ravens run an impressive table.
Think about it: Through 196 minutes and 42 seconds -- including a double-overtime affair in polar-bear cold conditions in Denver -- Flacco has been as good as any quarterback could hope to be when it has mattered the most.
Birk, who is in his 15th season as an NFL center, joined the Ravens four seasons ago, before Flacco's sophomore campaign. He said he's witnessed steady improvement.
"He continues to get better and continues to get better," Birk said. "The great thing about playing with Joe and just being with him: Nobody is less impressed than Joe with what he does."
It is no act. Flacco's own father, Steve, has called him boring. Joe said his dad views that as a compliment, meaning that he carries himself properly. It's not as if the son would argue, anyway.
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"I don't know if I'd say I'm dull," Joe said, "but I'm probably close to it."
Flacco, however, isn't afraid to speak his mind. During a radio interview last spring, he agreed that he is a "top-five quarterback," adding, "What do you expect me to say?" (That seems prescient now, doesn't it?)
On the tired topic of whether he is elite, Flacco said this week, "I don't really care. To be honest with you, it's kind of a crazy question; it's weird to answer. I'm just going to let my play speak for itself."
When asked about the notion of a cold-weather Super Bowl, Flacco made it clear that while he believes the Ravens are built to win in such conditions, he's not in favor of it. "Imagine," Flacco said at Tuesday's media day, "being in Giants Stadium next year doing this in 10 degree weather. Have fun." (The venue that the New York Jets and New York Giants call home is known as MetLife Stadium, and media day will be held indoors when Super Bowl XLVIII is played there. But you get the idea.)
Flacco isn't afraid to bank on himself, either. After he and his agent, Joe Linta, turned down a contract extension in August, talks were tabled. Now, with this postseason under his belt, Flacco can command a deal that matches every definition of elite.
Flacco has said he knows the contract will work out, and he expects to play in Baltimore. He certainly doesn't play like someone burdened by the situation.
"I doubt he thinks a lot about it," Birk said. "I know he loves to play football, obviously. He's a great competitor. Joe is just one of those guys. He doesn't (even) have to warm up to throw the ball a mile. He's one of those guys. He was made to be an NFL quarterback."
The script of Flacco's story is much like Eli Manning's with the New York Giants. Flacco has long received more respect inside his locker room than outside of it. Both Flacco and Manning are sometimes viewed -- incorrectly -- as being too meek or lacking fire. Two Super Bowl championships have changed that for Manning. One would for Flacco.
There's another similarity with Eli: Flacco provides invaluable leadership in the locker room, even if his voice is never the loudest.
"My way is to develop a relationship with the guys, gain their trust and go out there and play well and continue to do it over and over again," Flacco said. "That's the bottom line."