How can a backup QB be a leader? nyj Dan Leberfeld

Darrelle Revis had this to say about Tim Tebow –

“He’s a born leader, he really is,” Revis said. “Very few athletes have the gift he has. He tries to lead by example all the time. He tries to be positive, which is awesome, and that (has resulted) in his success on the field.”

But this begs the question – how can a #2 QB be a leader?