The Oakland Raiders have signed free agent quarterback J.T. O'Sullivan, Paul Gutierrez of CSNCalifornia.com reports.

Today's signing likely spells the end of the season for quarterback Bruce Gradkowski, who suffered a third-degree separation of his right shoulder in Sunday's loss to the Miami Dolphins.

O'Sullivan, 31, has completed 56.4% of his 257 pass attempts for 1,866 yards, with 9 touchdowns and 13 interceptions during an 8-year career that began as a sixth-round pick (186th overall) out of UC-Davis by the New Orleans Saints in 2002.

O'Sullivan's NFL odyssey has included stints with the Green Bay Packers, Minnesota Vikings, New England Patriots, Carolina Panthers, Detroit Lions, San Francisco 49ers, Cincinnati Bengals, and most recently, the San Diego Chargers.