The Oakland Raiders continued to rebuild their defense with the signing of Atlanta Falcons free agent defensive tackle Vance Walker.

Oakland has now added six free agents, and all of them are on the defensive side of the ball (three linebackers and three defensive linemen).

Walker is considered a rotational player more than a starter, but he could get a chance to start. He is solid against the run and he is a versatile player overall.

Meanwhile, the NFL Network has reported Oakland has interest in Tampa Bay tight end Kellen Winslow. Winslow, who’ll turn 30 in the summer, played just a few snaps in 2012. He is recovering from a knee injury. In the past, he has been a productive player, but his injury history is a concern. The Raiders have a hole at tight end with the departure of Brandon Myers -- who had 79 catches last season -- to the Giants.