"The two [first-quarter] interceptions and then eight plays not getting anything [at the end of the game]. I'm disappointed I didn’t do a better job in those...spots especially," Rivers said after the game, per Steve Kroner of the San Francisco Chronicle.
The Chargers got the ball down two with about one minute remaining but the quarterback threw seven straight incomplete passes, only getting a first down on a defensive holding. The eighth play ended with an interception on fourth down to seal the loss.
Of course, Rivers put his team in an early hole with interceptions on his first two drives of the game, the second of which was returned for a touchdown to give the Raiders a 10-0 lead.
The veteran finished with two touchdowns but had just a 57.5 quarterback rating thanks to his three turnovers.
In addition to losing a key divisional game, Rivers was also upset at the result of what is likely his final outing in Oakland with the Raiders moving to Las Vegas next year.
"It was obviously not the way you wanted to end your time coming here," he said. "It was one of the last-standing, last few active old-school NFL stadiums, kind of one of the originals."
Even as a visiting player, he appreciated the fans during the prime-time battle.
"The atmosphere tonight was awesome," he added. "Just disappointed we didn't play better and find a way to win."
The 37-year-old is quite familiar with the Coliseum, starting there once every season since 2006. According to Josh Dubow of the Associated Press, only nine Raiders entered the day with more appearances in their home stadium than Rivers had as a visitor.
He won't go out on a high note, though, unless the two teams have an unlikely meeting in the postseason.