Kansas City Chiefs starting defensive end Frank Clark is out for Sunday’s game against the Los Angeles Chargers with a hamstring injury, sources told ESPN’s Adam Schefter.

Clark strained his hamstring in practice on Thursday and was listed as doubtful to play. Coach Andy Reid said it was a separate hamstring injury from the one that kept Clark out for Kansas City’s regular-season opener.

The Chiefs are optimistic that defensive end Chris Jones, 27, will play Sunday, sources said. Jones was listed as questionable with a wrist injury he suffered in last week’s loss to the Baltimore Ravens.

Clark, 28, played 70% of the Chiefs’ snaps on defense last week and recorded two tackles.