The Oakland Raiders have had a lot of success during their history because of players they have drafted, but they have had some impact players that they signed during free agency. There have been some busts in free agency like Michael Crabtree, who many believed would become a Hall of Famer in the black and silver, but that didn't pan out. There have been some who have changed the face of the franchise in a good way.

Let's look at the five best free agent signings in Raiders franchise history.

5. Jerry Rice

Jerry Rice came to the Oakland Raiders when he was supposed to be washed up and at the end of his career. He proved a lot of people wrong, playing 54 games putting up 3,286 yards and 18 touchdowns.

He, along with Tim Brown, were quite the one-two punch, and caused a lot of issues for opposing defenses.

4. George Blanda

George Blanda was a kicker and the quarterback during the early parts of his career, but by the time he signed with the Raiders, he wasn't slinging the pigskin anymore.

Blanda kicked his way to 863 points during his eight years with the Raiders and he was a big reason for their success while he was in town.

3. George Plunkett

If George Plunkett's stats would be even a little better, he would be the top free agent signing. With the Raiders, Plunkett threw 80 touchdowns and 81 interceptions.

Even with the subpar stats, Plunkett led the team to the Super Bowl in 1981 and 1984 and that is what he will always be remembered for. For quarterbacks, it all comes down to Super Bowl wins and he got the job done.

2. Charles Woodson

This one is a bit strange because the Raiders drafted Charles Woodson, but he did leave from 2006-12 going to the Green Bay Packers. When Woodson was deciding where he wanted to finish his career, many believed he would go try to win another Super Bowl, but he decided to come back home, and that helped usher in a new era of Raiders football. He was a great leader for Khalil Mack and Derek Carr.

Even though he had lost a step on the field, what he did in the locker room can't be ignored. The Raiders probably wouldn't be where they are right now if it wouldn't have been for Woodson coming back.

1. Rich Gannon

This one is pretty easy, and there isn't much debate. Rich Gannon is the greatest free agent signing in the team's history. The Raiders signed Gannon in 1999 and he quickly became one of the better quarterbacks in football. He was voted to the Pro Bowl in his first year and it only went up from there. In the four years he was the Raiders' starter, he threw for 5,787 yards and 105 touchdowns.

In 2002 Gannon won the MVP award and led the Raiders to the Super Bowl. Even though he struggled in the Super Bowl, that can't take away from how important Gannon was to the Raiders. Gannon never has to pay for a meal in Oakland and he will always be considered one of the best in team history.