No more clear example of this can be seen than in the recent stories coming out of Super Bowl Champion Seattle Seahawks pre-season training camp. Head Coach Pete Carroll spent the off-season studying tackling and turned to rugby for lessons to implement with his already top ranked defense. He's noted the effectiveness and safety of rugby tackling technique. Ruggers on our high school teams may recognize some of the drills used.
Carroll even released his own instructional video, embedded below: Video It's worth taking a look!
There's also an article on Pro Football Talk about how "the smartest in the game of football are going back to it's roots"