Cumberland earlier announced the news on Instagram.
With 8:42 left in the second quarter, Cumberland pulled up short near the back of the end zone after accelerating to catch a deep ball thrown by quarterback Kellen Clemens.
Cumberland, 29, had to be helped off the Qualcomm Stadium field, and he was taken on a cart to the locker room for further evaluation.
It will be an uphill battle for Cumberland to return to the field. While with the New York Jets, Cumberland suffered an Achilles tendon tear in 2011 that forced him to miss most of that season.
The Chargers also lost guard Donavon Clark, a seventh-round selection in this year draft, for the season after he suffered a right ACL injury that forced him to leave the second half of Friday's game, which the Chargers won 19-3.
Clark had been working with the second unit at both guard positions, an area of focus for San Diego, which had injury concerns along the offensive line last season.