Johnston is slated for a larger role on offense with Mike Williams (knee) having suffered a season-ending ACL tear, Ian Rapoport of NFL Network reports.
Johnston has played less than 25 percent of offensive snaps in each of the Chargers' first three games this season, but he'll need to step up quickly for the passing game with Williams, an every-down player, done for the year. The rookie first-round pick profiles particularly well as a deep threat, which makes him both an ideal fit for Justin Herbert's arm talent and as a complement to Keenan Allen, but he has yet to flash that explosiveness at the NFL level. Sunday's upcoming matchup against a struggling Raiders secondary could set the stage well for Johnston to take advantage of his new opportunity, however. Meanwhile, Joshua Palmer also figures to step into a larger spotlight in the wake of Williams' injury.