The NFL actually has some former rugby players in its ranks already. Baltimore Ravens defensive tackle Haloti Ngata and Seattle Seahawks defensive tackle Jesse Williams both played rugby before college football. Former New York Jets tight end Hayden Smith had a cup of coffee in the NFL before heading back overseas for the Saracens Football Club. Former Olympic discus thrower Lawrence Okoye also has a rugby background and is currently on the San Francisco 49ers practice squad.
The fastest man in international rugby, Carlin Isles, spent a short time on the Detroit Lions practice squad (reportedly running a 4. 2 40- yard dash while he was there), but has since gone back to Scotland to join the Glasgow Warriors. So, this sort of thing has been done before —it's lightly charted waters instead of completely uncharted. Smith talked a bit about making the switch with The Daily Telegraph's Gavin Mairs: The biggest problem may actually be that his skills are anachronistic to the NFL's current makeup.
Former Bleacher Report writer and current Football Outsider Scott Kacsmar looked at the impact of the NFL's move of kickoffs to the 35-yard line in 2011 and found that between that move and the end of last season, only 51. 5 percent of kickoffs have been returned. Last season, that number was 48 percent.
Even when you add a few punt returns per game, it's clear that pure returning specialists are becoming an endangered breed. Hayne will likely need to find other ways to make himself useful. His toughness and physicality would be a plus on the opposite side of special teams as well. He's big, at 6'2", 220 pounds, so if an NFL team can teach him to hit like an NFL player, he could be an impact gunner on a kick or punt coverage.