KIRKLAND, Wash. - A sore back left Seattle's Chris Gray unable to practice Sunday, so second-year guard Steve Vallos filled in at center on a reshuffled starting offensive line.

Gray went down during practice Saturday afternoon with a back injury and club officials said he had tightness in his back Sunday. The 16-year veteran is expected to back up Rob Sims at right guard this season but has been the first-team center while starter Chris Spencer recovers from shoulder surgery.

For now, the position belongs to Vallos, who started at tackle in all 48 games he played in at Wake Forest but is switching to guard-center in the NFL. He spent last season on Seattle's practice squad.

Defensive end Patrick Kerney and offensive tackles Walter Jones and Ray Willis were among those who participated some in the morning then took the afternoon off.

Seattle avoided a possible scare when quarterback Matt Hasselbeck had an awkward step on his drop back during the morning practice and limped away. After a few minutes, Hasselbeck walked off the field without problems and was back for the entire afternoon session.

MOUNT MIKE: It was a bit on the cool side Sunday morning with temperatures in the low 60s, but coach Mike Holmgren was running red hot. The Seahawks' first practice in full pads was filled with crashing helmets and shoulder pads, plus Holmgren's growly voice of exasperation an underperforming offensive unit. At one point, after chewing out a few players, Holmgren dipped his head, chin to chest, following another bumbled play.

Holmgren was in better spirits in the afternoon following a much improved offensive effort.

QUICK HITS: Some players get a little break Monday with the afternoon practice devoted to special teams for the first time. That follows three days of full squad practices in the morning and afternoon. ... WR Jordan Kent, expected to face tight competition for a roster spot, commented on his dad, Ernie, getting a contract extension as basketball coach at Oregon, "It's never bad to have job security." ... On the first day of full pads, the best hit belonged to rookie Jamar Adams from Michigan, who drilled fellow rookie tight end John Carlson, forcing a fumble.