I always think that the fullback (when called into action) has the toughest defensive job of all, defending linebreaks against him, while also in-goal grubbers, bombs etc (along with wingers). If you're fullback is suspect in defence, once your line is broken, goodnight. He doesn't always have to make the tackle, he can also herd the attackers just enough to allow his defence to catch up. Two different styles of defence.
In the line - Bowman.
Fullback - Patten & Peachey (yes, peachey)