Background: Affirmed (February 21, 1975 - January 12, 2001) was an American Thoroughbred racehorse who was the eleventh winner of the United States Triple Crown of Thoroughbred Racing. Affirmed was also known for his famous rivalry with Alydar, whom he met ten times, including in all three Triple Crown races. Affirmed was the last horse to win the Triple Crown for a 37-year period, which was ended in 2015 by American Pharoah. Affirmed won fourteen Grade
Context: Affirmed returned to racing in early August in the Jim Dandy Stakes at Saratoga. He nearly became an upset loser to the front-running Sensitive Prince but closed in the last 100 yards in a race that Laz Barrera considered one of Affirmed's finest efforts. Alydar and Affirmed met once more, in the Travers Stakes at Saratoga. Affirmed, piloted by Hall of Fame jockey Laffit Pincay substituting for the injured Cauthen, cut off Alydar entering the far turn, causing his rival to hit the rail and almost go down, losing six lengths before recovering his stride. Affirmed finished first but was disqualified and placed second. The horses never met again, and the final winning tally stood at Affirmed 7, Alydar 3. 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 4/5 for the one-turn mile and 1/8. 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. As a three-year-old, Affirmed won 8 of 11 starts with 2 seconds and 1 unplaced run, for earnings of $901,541. He was named Horse of the Year despite the losses to Alydar, Seattle Slew, and Exceller, and was also named the American Champion Three-Year-Old Male Horse.
Question: What did he do after the triple crown?

Answer:
The 1978 Marlboro Cup Invitational Handicap marked the first time in racing history that two Triple Crown winners ever met