Which of these Triple Crown winners was NOT also 2-Year-Old Champion the previous year?

Which of these Triple Crown winners was NOT also 2-Year-Old Champion the previous year?

Which of these Triple Crown winners was NOT also 2-Year-Old Champion the previous year? [1112 votes total]
Affirmed (219)	20%
Assault (345)	31%
Citation (105)	9%
Seattle Slew (136)	12%
Secretariat (307)	28%