It's Sunday, 8-year-old Billy's favorite day of the week. Why? Because today is his day to play. He's been eyeing his hanging cleats with anticipation, eagerly counting the days: Monday, Tuesday, Wednesday. As the week progressed (to him, at a seemingly glacial pace), Billy was dreaming of running, passing, and tackling--the thrill of a game that fuels him to conquer anything and everything the third grade might throw his way.

Think Billy's dreaming about football, right? Guess again.

Billy is one of the 2.1 million kids in the U.S. who play rugby.

Shocked? So were the participants in a recent social media poll.

I asked followers to guess the "fastest-growing sport in the U.S. today," and 96 percent of the voters were completely unaware. The vast majority guessed soccer, with lacrosse a close second.

Rugby, known to novices as football without pads, is a sport played professionally in 120 countries. It ultimately gained its establishment here through American colleges and universities. Today, its massive expansion has stimulated the formation of youth leagues across the country. While participation in football and baseball has been declining steadily for years, rugby enrollment grew 81 percent from 2008 to 2013, beating out lacrosse and hockey--one of many reasons why the Sports & Fitness Industry Association ranked rugby as the fastest-growing team sport in the U.S.

Surveys and rankings aside, let me tip you off to the most critical growth metric of all: Rugby is becoming part of pop culture. Yep, that game involving scrummages, rucks, mauls, and passing backwards has seeped its way into cultural conversations. Given rising rates of safety concerns in football, the pursuit of sports with equal participation opportunities, and the allure of an upcoming trend, there's a new oval-ball game in town, and it's got infectious influence. Here's why.

Big Ben was searching for a rugby ball--and couldn't find one

ESPN reported this week that Pittsburgh Steelers quarterback Ben Roethlisberger prepared for his match against the Philadelphia Eagles by throwing a rugby ball during practice. Unfortunately for Big Ben, finding one wasn't easy. About two years ago, Roethlisberger asked equipment managers if he could practice with a rugby ball. At three centimeters longer and two ounces heavier than a football, "[using a regulation rugby ball] makes the actual ball feel smaller for practice," according to Roethlisberger. Field manager Patrick Noone said the team looked everywhere--Dick's Sporting Goods, Target, etc., and couldn't find one to purchase. They eventually discovered BSN Sports out of Pittsburgh. Thirty-three dollars later, Roethlisberger's new warmup regimen was born. Less than 24 months later, retailers (including Dick's) have stocked up.

Vogue and Vanity Fair are talking rugby

As women's rugby made its Olympic debut this summer in Rio (while the men returned for the first time in 92 years), Vogue and Vanity Fair--known for their fashion-forward, provocative covers, celebrity portraits, and gossip columns--took a pause to feature an array of Olympic athletes headed for Rio.

Vogue covered the USA Rugby Women's Sevens team, with the provocative caption, "Will Women's Rugby Be the Next Women's Soccer in the U.S.?" With heroes like Carli Lloyd championing the game of soccer, rugby, too, offers a playing field for women. The sport boasts the exact same rules for women and men, exact same ball, and exact same field size. With more than 20,000 registered females in USA Rugby, the U.S. has more female rugby players than any other country. As contact sports among females scale, rugby, a traditionally male-dominated sport, breeds opportunities for multiple markets.

NBA's and NFL's top athletes credit rugby for their game

The NBA's number one draft pick, the Philadelphia 76ers' Ben Simmons, credits much of his basketball game to skills he learned playing rugby.

Simmons, an Australian native, played rugby in grade school. He stopped playing once it came time to focus solely on basketball. Simmons has, however, found that the skills from rugby translate to the basketball court. As a point forward, he has keen floor vision and savvy playmaking abilities--averaging 4.8 assists per game in college and 5.5 per game in summer league action.

"Passing, spacing, team-oriented sports helped me," the Sixer said.

Simmons isn't the only one. The New England Patriots' Nate Ebner recently made history by becoming the first active NFL player to compete at a Summer Olympics to fulfill his dream of playing rugby in Rio.

As rugby relationships among elite athletes emerge, the visibility is further fueling the sport's ambitious growth.

The eyes are already watching

Since the 2009 announcement that rugby would be admitted into the Summer Olympics, the sport has experienced increased TV exposure. NBC has been broadcasting several rugby tournaments, particularly the Collegiate Rugby Championship (now sponsored by Penn Mutual, called the Penn Mutual CRC), each year since 2010.

In 2011, more than 5.4 million viewers tuned in to watch the USA Sevens on NBC, helping increase awareness for rugby. Viewership for the 2012 USA Sevens earned successful ratings (0.7), beating those for an NHL match (0.4) and five college basketball games (0.1-0.3) played that same weekend. NBC also broadcast several matches from the 2011 Rugby World Cup, marking its first live broadcast on TV in the U.S.

In addition to network TV, cable channels are also broadcasting an increasing amount of the sport.