PITTSBURGH — Backup linebacker James Harrison signed a $5.5 million, four-year contract with the Pittsburgh Steelers on Thursday, even though he would not have become a free agent until 2008.

Harrison received a $1.375 million signing bonus.

Normally, NFL teams do not offer such terms to backup players who can cannot become free agents for several more seasons, However, Harrison had 45 tackles and three sacks last season for the Super Bowl-champion Steelers and he started three games.

The 27-year-old Harrison was not drafted after playing at Kent State. But he made the Steelers' roster in 2004.

Steelers coach Bill Cowher has talked repeatedly about Harrison's ability to make plays when he has filled in for injured starters, including a month-long stretch last season following outside linebacker Clark Haggans' knee operation.