According to an Associated Press article:
Yale quarterback Patrick Witt has decided to give up the opportunity to compete for a Rhodes Scholarship so he can play against Harvard. Yale said Witt, a finalist, had withdrawn his Rhodes application because the interview was scheduled for Saturday, the same day as the Harvard game.
In 1947, for instance, then Harvard student Robert F. Kennedy, who had broken his leg in practice, played for the last few minutes of the The Game in a cast. Harvard football players had to be in the Yale game in order to earn their varsity letters.