Why do you think the little giant is an underdog? Because he is only there to deceive the blocks and has no other uses and does not have the fame of an ace?
My guess is that he chose that guy at first because he's short like he is, then he understood the guy was actually efficient. He also had fun and was an integral part of the team, probably even a leader. Since our red head has a size complex, I can understand why he wanted the little giant as a role model.