"We just feel like it's important for the game," Carroll said. "We're trying to always help out, in particular in keeping the game safe. We've been doing something for a long time that we had never really shared before. It was something we had learned, just through ball—it's an old style concept of tackling. When we connected it with rugby, it made it even more fun to grow with it."

This year's video features many of the same techniques from last year's version, but adds a few elements such as what they call the "Hawk lift tackle"—essentially the idea being that a runner can't drive his feet for extra yardage if those feet are no longer in contact with the ground. If last year's video is any indication, the second edition should be well received by everyone from Pop Warner coaches to high school coaches to NFL league officials promoting player safety.

"We've gotten great response from a lot of coaches in a lot of places," Carroll said. "The league in particular really liked that we were putting this out there. We'll pump it all out again… and it will reach thousands of coaches who connect with tons and tons of people. We're just hoping we can keep the game fresh and keep moving."

Carroll and Seto have seen a significant change in the way their players tackle in just the short time that this has become a coaching emphasis for them. Kam Chancellor, for example, was penalized and fined multiple times early in his career for helmet-to-helmet hits, even giving himself a concussion in 2011 with a hit on Anquan Boldin. Now, Chancellor makes highlight-reel hits with his shoulder and is still one of the most intimidating forces in the game.