Allen (hamstring) has been ruled out for Sunday's game against the Falcons, Lindsey Thiry of ESPN.com reports.
The same applies to fellow starting wideout Mike Williams (ankle), which leaves Joshua Palmer (concussion), who is slated to play Sunday, per Jeff Miller of the Los Angeles Times, and DeAndre Carter (illness, questionable) -- if available -- to lead the Chargers' Week 9 wideout corps. Allen's next chance to suit up will arrive Week 10 versus the 49ers on the road.