Chad Brown, a Pro Bowl linebacker for Pittsburgh 10 years ago, was signed Thursday by the Steelers to add depth and experience at what suddenly has become a depleted position. The Super Bowl champions (1-3), losers of three in a row, added the 36-year-old Brown a day after Pro Bowl linebacker Joey Porter injured a hamstring during a routine indoor practice for Sunday's home game against Kansas City (2-2). Porter is listed as questionable.