The Panthers have signed defensive tackle Darwin Walker to a one-year deal.  A Charlotte newspaper says the pact may be worth over one-million-dollars with incentives.  Walker was limited to 11 games due to injuries last season and collected 17 tackles and one sack for the Chicago Bears.  The 31-year-old South Carolina product spent the previous six years in Philadelphia, where he collected a career-best 42 tackles in 2003.