Ruiz has the higher confidence in this rematch since he already stopped AJ on their first encounter. And this is an immediate rematch. AJ dared without a break nor tune ups which is very risky career wise. But I don't think AJ quit on their first encounter. It was the referee that stopped it.
Ruiz was confidence because he has beaten Anthony before and is thought is that he have seeing Anthony's all while Anthony is not well prepared for the fight which is the reason why he ask for an immediate rematch to prove the first fight was just a fluke. Like you said, it very risky to his career and this is what make this rematch very important to him.
@mu_enrico, interview are just for evaluation and it can't 100% justify the result of the rematch.