Packers receiver Javon Walker's season hangs in the balance after he injured his right knee in the third quarter against Detroit on Sunday. "It was his ACL," Packers coach Mike Sherman said after the Lions won 17-3. Sherman said the team will not know how serious the injury is until Walker has an MRI on Monday, although the Green Bay Post-Gazette is reporting that Walker is expected to miss the rest of the season. Walker was hurt when he caught a 55-yard pass -- negated by a pass-interference call against him -- and was tackled by safety Terrence Holt.