Cory Withrow began the regular season in that role after Birk underwent season-ending hip surgery, but he was replaced by Melvin Fowler after four games. Fowler, though, struggled in the first half of the Giants game, missing a couple of calls, and was pulled at halftime because of the mistakes and a strained oblique muscle.
It's unclear if Fowler will be healthy enough, or have the confidence of the coaching staff, to be back at center Monday night against Green Bay. Fowler, listed as probable, has the greater upside, but Withrow might prove to be the safer choice to run things right now.
Either way, the Vikings are getting a weekly reminder of just how valuable the cerebral Birk has been and just how much they had come to rely on him.
Right now, that is part of the problem. Coach Mike Tice and offensive coordinator and line coach Steve Loney have made it clear that the remaining members of the line must rely less on Withrow or Fowler and take it upon themselves to identify their blocking assignments.
At running back, Mewelde Moore is expected to return to his role as the Vikings' starter Monday after not getting on the field for an offensive play against the Giants because of a sprained right wrist. Moore had to wear a brace on the wrist, something that would have prohibited him from carrying the ball in that hand, but he was able to return punts.
Moore's injury gave Michael Bennett the majority of the rushing workload, but with the Giants stacking the line of scrimmage in order to stop the run, he gained only 16 yards on 19 carries.
The changes at running back go past the starting job. With Moe Williams missing the rest of the season because of a knee injury, rookie Ciatrick Fason stands to be the running back on third-and-1 and goal-line situations for the rest of the year.
At receiver, don't be surprised to see Koren Robinson's role increase. Robinson caught a 44-yard pass against the Giants, and with Nate Burleson obviously not playing at 100 percent, the Vikings might be inclined to turn to Robinson as a go-to guy. He has the big-play ability the Vikings sorely need with Randy Moss no longer around.