It was a sour end to the regular season for the NFC West champion Cardinals (13-3), who already had clinched the NFC's No. 2 seed and a first-round playoff bye.
Tyler Lockett set up three of Seattle's four first-half touchdowns - with punt returns of 66 and 42 yards and a 36-yard reception.
Seattle will play at Minnesota in the wild card round next weekend.
Copyright 2015 by The Associated Press