RENTON, Wash. - Marcus Trufant's season is being cut short for the Seattle Seahawks after back problems that sidelined him for nearly half of the 2009 season flared up.

Trufant, Seattle's starting cornerback and the longest-tenured Seahawks player, was placed on injured reserve Monday as the team returned from a bye week. Trufant will be replaced in the lineup by second-year cornerback Walter Thurmond.

Trufant was originally thought to have a bruised sacrum - a triangular bone at the base of the spine - suffered at some point in the Seahawks' Week 4 loss to Atlanta. But the injury, which flared up during the middle of the week and not immediately after the loss to the Falcons, turned out to be more like a disk issue that caused him to miss six games during the 2009 season.

"It's the right thing to do. We've got to take care of him," Seattle coach Pete Carroll said. "It's a recurring back situation. We didn't realize it really is what happened before and so we've got to take care of him and he's going to be down for some time."

Carroll said the team was unclear at first about what Trufant's back issue was. He made the trip with the team to New York in Week 5 for the Seahawks' win over the Giants but was inactive and described by Carroll as being unable to bend over and tie his shoes.

Trufant has spent all his nine NFL seasons in Seattle.

Originally drafted 11th overall out of Washington State in 2003, Trufant has started 123 of 124 career games. Carroll said the hope is that his back can be treated without needing surgery.

Thurmond started in Trufant's place against the Giants.

"I've been ready since I came into camp," Thurmond said. "Things didn't go as planned, but there is always a plan so I'm going to keep preparing and get ready for next week."

Aside from Trufant, the Seahawks are still unsure if starting quarterback Tarvaris Jackson will be available for Sunday's game at Cleveland after he suffered a strained pectoral muscle against the Giants. Jackson's done some limited throwing, Carroll said, but the Seahawks are moving ahead with the idea of getting backup Charlie Whitehurst ready to start against the Browns. They will insert Jackson into the game plan if he becomes healthy enough to play.

If the Seahawks go with their backup, it would be the second start of Whitehurst's career. He led Seattle to 13 points in the final 1 1/2 quarters of its 36-25 win over the Giants.

"We're going to get Charlie ready to go and get Josh (Portis) ready to play also. ... If Tarvaris jumps back into it, we'll figure out what that means," Carroll said. "At this point Charlie has to have his mind set on getting ready to play football. He went about the break in that manner."

Carroll is more optimistic about starting offensive linemen Robert Gallery and Max Unger's ability to play. Gallery has missed the past three games after suffering a groin injury that required surgery and is expected to practice on Wednesday.

Unger is slightly behind Gallery's timeline following a foot injury in the win over New York. Unger, who spent most of last week in a walking boot, probably will practice fully later in the week, Carroll said.

Tight end Zach Miller is also expected to practice Wednesday after taking a wicked hit from New York safety Kenny Phillips and injuring his neck.

"We wanted to make sure to maximize the off time," Carroll said. "(Miller) is still a little sore, sore neck but it looks like he has a chance to play."

To fill Trufant's roster spot, the Seahawks signed defensive tackle Jason Shirley and later Monday signed linebacker Stephen Franklin to take the spot of Jameson Konz, who was placed on injured reserve with a knee injury. The Seahawks were also awarded former USC running back Allen Bradford on waivers from Tampa Bay late last week and took the roster spot of linebacker Aaron Curry, who was traded to Oakland for a pair of future draft picks.