Rivers completed 5-of-7 passes for 116 yards, but no touchdowns.
Billy Volek went 6-for-7 for 66 yards with one touchdown.
Rookie Charlie Whitehurst went 5-for-9 for 52 yards.
Michael Bennett ran for a touchdown.
Legedu Naanee caught two passes for 54 yards with one touchdown, while Nate Kaeding added a field goal and two extra points for the Chargers, who bounced back from a 20-14 loss to the Seattle Seahawks last week.
Arizona quarterback Kurt Warner went 6-for-13 for 80 yards and one interception.
Tim Hightower rushed for 42 yards on nine carries, and Neil Rackers kicked two field goals for the Cardinals, who lost their pre-season opener.