Rivers completed 21-of-28 passes for 249 yards without an interception and Ryan Mathews added 103 rushing yards with a score on 29 carries for the Chargers (6-7).
The victory enabled San Diego to remain one game behind Baltimore and Miami for the final AFC wild card spot.
Eli Manning -- who was traded to the Giants after being chosen first overall by the Chargers in the 2004 NFL draft -- was intercepted twice for New York (5-8).
He made good on 20-of-32 attempts for 259 yards with a touchdown and Hakeem Nicks compiled 135 yards on five catches as the Giants were officially eliminated from playoff contention.
Celebrity Families of 2014 [PHOTOS]