When free agency first began, teams salivated at the thought of the quick fix a free agent can bring. There are certainly examples of that happening. The Packers shored up their defense for years by signing Reggie White . The 49ers fueled their '94 championship drive with Deion Sanders , Tim McDonald and Ken Norton , among others, and when the Cowboys grabbed Sanders the next year, he helped make their last Super Bowl possible. But too often, teams have learned that it's not that easy to just plug in free agents.
Football is a game of systems, and a player can look good in one system and bad in another.
Again, an example from the 49ers. Winfred Tubbs was an outstanding linebacker in New Orleans because the Saints allowed him to roam on the outside and use his natural athletic ability to make plays. When he came to the 49ers, he played inside and was not the impact player the 49ers had expected. The other problem with free agency is that players often have played their best football before they became free agents. What a team sees in a player before he becomes a free agent is not necessarily what it gets from that player.