Something in which i supposei can weigh in. Neither Bennett or Graham played rugby, they played Australian Rules, which is mostly kicking, played on grounds 150 metres long. Hence why they had the skills to become NFL punters.
Rugby is probably closer in it's general gameplay, there are positions that would be the equivalent across the two sports, although loosely. I suppose linebackers would be similar to the "back row" or "loose fowards", those with 6, 7, 8 on their backs. Their job, among other things, is to own the Five Eight (the field general, like the QB) whenever possible.
The outside backs would be the ones with the most potential to cross over, they're physically quite similar. I think i recall that former NZ winger Jonah Lomu was being chased by NFL scouts in his heyday 10 years ago. 6"5, 265. ran the 100 in under 11.
http://en.wikipedia.org/wiki/Jonah_Lomu
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