Linemate Anthony Herrera describes Vikings center John Sullivan as a "cool, laid-back, typical offensive lineman, very intelligent, a Notre Dame guy."

Sullivan will make his first regular-season start at the Metrodome today, replacing Minnesota native Matt Birk. Birk's departure for Baltimore would have seemed to leave a large physical and intellectual hole in the middle of the Vikings' line.

"That's life in the NFL," Herrera said in the Vikings locker room earlier this week. "People get over it pretty quick in here, but it is difficult. Extremely difficult. You're coming up after a Pro Bowler, who might be the best center we've had here.

"That's taking nothing away from Jeff Christy and Mick Tinglehoff, but to me, Birk is the best center the Vikings have ever had. So there is a lot of pressure on Sully, but I think he is doing a great job with it. He's taking on the responsibility and he's moving on. There is no shyness to him."

Brett Favre's arrival rendered most other Vikings story lines moot for the last month. Had Favre decided to stay retired, Sullivan's first Metrodome start would have been the story of the week at Winter Park.

His is not a bad story, even if he can't match the Meanderin' Mississippian for diva-ness and drama.

Sullivan grew up in blue-blooded Greenwich, Conn. "We were fortunate," Sullivan said. "I don't think anybody, if you saw the circumstances we lived in, would think we were rich. I didn't get everything I wanted as a kid. We drove used, crappy cars.

"But there's a lot of money around that town."

Sullivan played water polo and rugby and won state titles as a wrestler, and became the Connecticut football player of the year as a senior. Notre Dame coach Ty Willingham, the former Vikings assistant, recruited him.

"I had a lot of options coming out of high school," Sullivan said. "I could find a reason to say no to every other place. Ultimately, it came down to wanting to be able to say for the rest of my life that I played football at the University of Notre Dame.

"Ty was a very put-together guy, a good football coach. He ran the team well and with a lot of integrity. He's a guy who, when he spoke to you, you felt you could trust him, and that's a big thing with coaches. You want to know what you're getting yourself into."

Willingham got fired, and Charlie Weis took over. "I learned so much about the game of football from Charlie that I appreciate that I played for him," Sullivan said. "I don't think any of his former players would tell you that he's the easiest guy to play for. He comes from the Patriots' mentality, where if you do a great job that's what you were supposed to do, and if you don't do a great job you're going to get screamed at."

Sullivan seems more comfortable with his current coach. Brad Childress and Birk had their battles, and Childress seemed comfortable with the idea of replacing Birk with Sullivan, the Vikings' sixth-round pick in 2008.

Childress and Sullivan have both grown thick beards. Childress' looks like the precursor to a comb-over; Sullivan's provides a home for confused birds.

"It's just coincidental," Sullivan said. "But it would be no competition if it were a competition. My beard is about three times longer than his."

It's difficult for laymen to tell how much difference a center makes. The Ravens have been prolific offensively with Birk snapping to Joe Flacco; the Vikings haven't been shabby, either.

I texted Birk the other day, saying it was obvious he was the key to Flacco's success. Birk texted back: "Now you're talking!"

Birk is listed at 6-4, 309 pounds. He seems much bigger than Sullivan, who is listed at 6-4, 301.

"I can be a little deceiving," Sullivan said. "I don't look like the biggest guy, but I have big legs, and I'm pretty dense. Physically."

Today's a big day for Sullivan. He'll be the other guy in your cellphone photo of Favre.

Jim Souhan can be heard at 10-noon Sunday, and 6:40 a.m. Monday, Tuesday, Thursday and Friday on AM-1500. His twitter name is SouhanStrib. • jsouhan@startribune.com