The Chargers have struck in free agency. After more than seven hours passed quietly, they agreed to terms Tuesday night with Donald Brown, sources said. The former Colts running back joins San Diego on a three-year deal worth $10.5 million, $4 million of which is guaranteed. It is the same general structure to a contract running back Toby Gerhart reached earlier Tuesday in Jacksonville. Brown joins Ryan Mathews and Danny Woodhead atop the Chargers' rotation at running back. The latter two are entering the final seasons of their contract. This addition gives San Diego some protection. In January, its backfield was exposed during a playoff loss to the Broncos, unable to run the football when Mathews exited with an ankle injury. Brown is more suitable than Woodhead to run between the tackles. At 5-foot-10 and 210 pounds, he had 102 carries for 537 yards and six touchdowns in 2013. He also caught 27 passes for 214 yards and two scores.