The Chargers had already ruled out running back Ryan Mathews with a high ankle sprain. Wide receiver Keenan Allen is also out with a broken right collarbone and center Chris Watt is inactive after dealing with a calf injury.
Trevor Robinson will be the fifth center to start for San Diego this season.
Smith was ruled out Friday after tests showed a lacerated spleen, leaving Chase Daniel to make his second NFL start. Coincidentally, he started last season's finale against San Diego.
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