Conversation so far:
What was the biggest race Affirmed won in 1977?
Affirmed won his first start in a maiden special weight race at Belmont Park on May 24, 1977.
What was his time?
He followed up with a win in the Youthful Stakes on June 15 where he defeated Alydar by eight lengths.
How fast did he run at the Belmont Park?
CANNOTANSWER.
Where did he race after the Belmont?
On July 6 in the Great American Stakes, Alydar evened the score with a  3 1/2 length win after mounting a powerful stretch drive.

Question: Was Alydar his biggest rival?
Self-contained rewrite: Was Alydar Affirmed's biggest rival?