"Eddie Lacy beat me out there," Richardson said. "He had a few more touchdowns than I did."
Rivers led the Chargers to a wild-card playoff spot with four straight victories to close out the schedule, giving them a 9-7 record. He led the league with a 69.5 completion rate and threw for 32 TDs against 11 interceptions.
He received 13 votes in balloting so widespread that 12 players got votes. He was not at the awards show at Radio City Music Hall.
Chicago cornerback Charles Tillman won the Walter Payton Man of the Year award, and accepted the honor with tears in his eyes.
"As a Chicago Bear, this award has a special meaning to me," Tillman said.
AP Sports Writer Dennis Waszak Jr. and Pro Football Writer Howard Fendrich contributed to this story.
AP NFL website: www.pro32.ap.org