The Dallas Cowboys have won five Super Bowls and some of the free agents they have signed over the decades have been reasons why. Let's breakdown the five best free agents signings in Cowboys history.

Ray Donaldson

Ray Donaldson didn't join the Cowboys until the 1995 season when he was 36 years old, but he was a big reason they were able to win the Super Bowl that year.

Donaldson was the starting center for the 1996 season, shoring up a key hole on the offensive line. He didn't end up playing in the Super Bowl, but the Cowboys were still able to come away with a victory.

He played the 1997 season with the Cowboys and made the Pro Bowl. After that season, Donaldson hung up the cleats.

Ken Hamlin

Early in the 2000s, Ken Hamlin was a star safety for the Seattle Seahawks; later, he signed a one-year deal with the Dallas Cowboys. That season, Hamlin had a career-high five interceptions and the Cowboys rewarded him with a long term extension.

Hamlin played the next two seasons in Dallas as a key part of the secondary. Hamlin is often overlooked because he played only three years with the team, but he deserves recognition as a critical free agent signing.

Jay Novacek

Jason Witten is the best tight end in Cowboys' history, but sitting right behind is Jay Novacek. Novacek signed with Dallas in 1990, and he was a standout. Troy Aikman, Michael Irvin, and Emmit Smith get all the attention for what they did during that time, but Novacek was also important to the team's success.

In each of his first three seasons with the Cowboys, Novacek had at least 600 yards receiving. Novacek retired after the 1995 season.

Terrell Owens

There are a lot of opinions about Terrell Owens' time with the Dallas Cowboys, but he was a strong player and his impact on the organization is still felt.  Owens signed with the Cowboys before the 2006 season and he had three productive  years on the field for the team.

During the 2007 season, Owens played in 15 games putting up 1,355 yards and scoring 15 touchdowns. The Cowboys were able to win their first playoff game since the 1990s with Owens on the outside.

Winning is most important in the NFL and there is no doubt that Owens helped the Cowboys do just that.

Deion Sanders

There's no question that Deion Sanders is the top free agent the Cowboys have ever signed. There can be a strong argument that Sanders is the best cornerback in NFL history. Sanders signed with the Cowboys in 1995 and he played five seasons in Dallas.

Opposing quarterbacks mostly threw away from Sanders when he was on the field, but he still had 14 interceptions in his five seasons there. He made the team instantly better and it allowed the Dallas to completely change their approach to defense.