Bears coach Marc Trestman said on Tuesday he anticipated Peppers and wide receiver Brandon Marshall making their preseason debuts against the Chargers, but the veteran pass-rusher was a late scratch due to coaches' decision.
Peppers, who has been battling a minor hamstring injury the past week and a half, was on the field watching the rest of his teammates going through pregame warmups.
However, Marshall and defensive end Corey Wootton are in uniform and scheduled to see action with the Bears starters for at least one quarter.
Also sitting out for the Bears: running back Armando Allen (hamstring), linebacker D.J. Williams (calf), defensive tackle Henry Melton (concussion), wide receiver Earl Bennett (concussion), long snapper Patrick Mannelly (ribs), offensive tackle Jonathan Scott (knee), fullback Harvey Unga (ribs) and tight end Kyle Adams.
San Diego rookie linebacker Manti Te'o has previously been ruled out due to a sprained foot.