Conversation so far:
What was an most important part of Secretariat's racing career?
Secretariat was an American Thoroughbred racehorse who, in 1973, became the first Triple Crown winner in 25 years.
What race did Secretariat participate in?
Secretariat's record-breaking victory in the Belmont Stakes, which he won by 31 lengths, is widely regarded as one of the greatest races of all time.
Is there any interesting information about Secretariat?
During Secretariat's racing career, he won five Eclipse Awards, including Horse of the Year honors at ages two and three.

Question: Who was his trainer?
Self-contained rewrite: Who was Secretariat's trainer?