Published: Aug 10, 2012 12:18 AM EDT
Updated: Aug 10, 2012 6:31 AM EDT

SAN DIEGO (AP) - San Diego Chargers starting running back Ryan Mathews is expected to miss at least a month after breaking his collarbone in a preseason game against the Green Bay Packers Thursday night.

Mathews was injured on his first carry of the preseason in the first quarter and did not return to the game. He is expected to have surgery Friday morning and coach Norv Turner said he'll be out four to six weeks.

Mathews was involved in a car crash on Monday, but said he was only banged-up and was able to play Thursday.

Mathews, who replaced LaDainian Tomlinson as San Diego's feature back in 2010, ran for 1,091 yards and six touchdowns last season. He added 50 catches for 455 yards.