シアトルスルー
Affirmed then prepared to meet another major rival: 1977 Triple Crown winner Seattle Slew. The 1978 Marlboro Cup Invitational Handicap marked the first time in racing history that two Triple Crown winners ever met in a race. Seattle Slew was a speed horse and got the first quarter mile in 24 seconds under jockey Angel Cordero, who never allowed Affirmed to get close. Seattle Slew won by three lengths in 1:45 for the one-turn mile and . The two horses met once more, in the Jockey Club Gold Cup. This time, Affirmed was to be aided by his stablemate Life's Hope, who was entered in the race to extend Seattle Slew in the early stages. However, Affirmed's saddle slipped during the race, leaving his jockey with almost no control. He tired to finish unplaced for the only time in his career as Exceller and jockey Willie Shoemaker defeated Seattle Slew by a nose.