Matt Birk did not participate in Wednesday morning’s practice, and offensive coordinator Darrell Bevell said the All-Pro center was suffering from a stomach virus.

Rookie John Sullivan took Birk’s place with the starting unit.

“Whenever you’re out there, a lot is expected of you,” Sullivan said. “Especially when you’re working with the 1s.”

Bevell said Sullivan has progressed nicely through offseason workouts and training camp. He said that the team usually keeps just seven offensive lineman so Sullivan is also learning to play both guard positions.

“You have to kind of teach them that out of necessity,” Bevell said. “He’s picked it up very well.”

Birk is expected back at practice today.

Jackson’s progress
In previous seasons, quarterback Tarvaris Jackson said when he left the pocket, his first instinct was to run. He admits that has changed.

“Now when I get outside the pocket I’m looking to throw the football down the field first,” Jackson said. “Keeping my head up and my options open.”

Jackson has been seen at camp scrambling away from pressure — particularly from the blind side from defensive end Jared Allen. He’s hoping that leads to less risk and less chance for a turnover.

“When you’re young, you want to run all the time,” Jackson said. “I still like to run, but at the same time I’d rather have passing yards and touchdowns than rushing yards. And take as less shots as possible.”

Family time
Rookie linebacker Erin Henderson said he’s excited for Saturday’s preseason game at Baltimore, playing in front of friends and family near his hometown of Aberdeen, Md. He said that he and older brother E.J. Henderson will request 25 to 30 tickets.

“E.J.’s going (to pay),” Erin Henderson said. “I can’t afford it.”

Henderson has been moved to first team kickoff and punt coverage for Saturday, replacing injured Heath Farwell, and will play more as a reserve linebacker.

“I haven’t played in that stadium since the state championship game in high school,” he said.

Two-minute drill
The starting offense struggled in a two-minute drill against the No. 1 defense. On the first play, Chester Taylor fumbled, then a couple of plays later, Bobby Wade had a pass go off his hands. The drive ended with an incompletion in the end zone.