The market for backup running backs has been established. Brandon Jacobs settled for a one-year deal with the 49ers on Wednesday for less than $2 million. Any running backs still available shouldn't expect to get anything better. (We're talking to you, Cedric Benson.)
The Chargers have made it no secret they plan to sign one of those running backs. They need depth, but they don't need to spend because they believe they already have their premier running back on the roster.
Mathews can be a frustrating player to watch. He can look like one of the most complete backs in the league for long stretches, but he struggles to consistently stay healthy. There aren't many runners who can go inside and out and accelerate quite like him.