Fantasy football owners probably yelled “not again!” when they saw San Diego Chargers wide receiver Keenan Allen leave Sunday’s game against the Kansas City Chiefs with a knee injury. The fear is that Allen — who missed most of last season with an injury — has torn the ACL in his right knee, but the Chargers have not officially announced the severity of the injury. Here are five receivers for Allen owners to target via the waiver the wire and/or trade market to replace him. Travis Benjamin, San Diego ChargersBenjamin signed a rich free-agent contract with the Chargers in the offseason, and he’s now going to be th... NESN.com