Ingram suffered a hip injury in Sunday's 31-20 win over the Seahawks. He cannot return to game action for at least eight weeks, meaning the first game he is eligible to return is Week 11 against the Raiders. The Chargers have a Week 10 bye.
Teams are only allowed to place one player on the reserve-injured list per season.
The 25-year-old tore his ACL before last season, causing him to miss all but the last four games of the regular season and two postseason games. The 2012 first-round pick out of South Carolina has three sacks and three forced fumbles in his three seasons with the Chargers.
San Diego (1-1) visits the Bills (2-0) on Sunday.
- Chris Mascaro