(WNFL)- Both of Wisconsin's starting football centers are sitting out the Badgers' entire spring practice schedule in the wake of off-season surgeries. Dallas Lewallen and Dan Voltz shared the starting job last season. Lewallen is coming off a knee operation. Voltz has what's termed an "upper-body injury." Voltz, who will be a sophomore this fall, said practice might be a grind -- but it's more of a grind standing on the sidelines and watching. Lewallen aggravated a knee injury against Iowa last November. He said he's not 100-percent yet -- and if he could practice, he would. Right guard Kyle Costigan is limited this spring after his own knee injury. It gives offensive line coach TJ Woods the challenge of setting up a makeshift group. Walk-on Aidan McNamara and freshman Michael Deiter are now the centers on two units. Deiter is with the Number-One group.