Only two running backs have won the Heisman Trophy since 1999. Alabama's Mark Ingram captured the award during the Crimson Tide's 2009 title season and USC's Reggie Bush pirouetted and front-flipped his way to immortality in 2005.

There's a strong chance that a third running back will be joining that list in 2015, as the only thing certain in this muddled Heisman Trophy race is that there will be an anomalously large running back contingent in New York City next month.

It's too early to handicap the Heisman Trophy race with any degree of certainty, a lesson learned after many crowned Leonard Fournette as the winner before November. But it's not too early to declare 2015 the Year of the Running Back, as there could be four backs among the top five Heisman Trophy finalists this season.

Alabama's Derrick Henry is this week's presumed leader, something that could certainly change by the second week in December. Henry already has 19 rushing touchdowns and has likely secured at least an invitation to New York. While there, he's certain to be joined by an impressive tailback crew—Florida State's Dalvin Cook, Ohio State's Ezekiel Elliott and Stanford's Christian McCaffrey all have a great shot at being Heisman Trophy finalists as well. And before we completely disregard Fournette after back-to-back clunkers against Alabama and Arkansas, let's remember that he still leads the nation with 1,474 rushing yards. (And that's with one fewer game than Henry, Elliott and McCaffrey.)

There will likely be a quarterback or two joining them in New York with Oklahoma's Baker Mayfield and Clemson's Deshaun Watson the leading candidates. But it would be a surprise at this point if a tailback didn't win the trophy and the majority of the top five vote getters aren't running backs.

To show what a departure it is to have tailbacks so dominant as the best players in college football, consider that the last time three running backs were among the top five Heisman Trophy vote getters was back in 2006. Arkansas's Darren McFadden, West Virginia's Steve Slaton and Michigan's Mike Hart filled out the top five with Notre Dame quarterback Brady Quinn behind winner Troy Smith of Ohio State.

The top five of the Heisman voting surely isn't a scientific method of researching top tailbacks, but it does serve as a bellwether for the most dominant players of the season. The run of quarterbacks winning the Heisman and generally crowding the top five every year comes amid the rise of an era of football where tempo, spreading the field and wide-open passing games became the dominant style. Somewhere between Bush in 2005 and Oregon quarterback Marcus Mariota last year, pro-style and run-heavy offenses evolved from the norm in college football to outliers.

So how did we get here? How in the era of five wide and pass-happy coordinators and allergies to huddles did a college football rediscover its between-the-tackle roots? Is this evidence that there's momentum shifting back to multiple tight-end sets and run-first teams again becoming the convention in college football?

Well, there's a handful of explanations and it depends on who you ask. Arkansas coach Bret Bielema said on Sunday night that "there's absolutely a shift" and that he thinks "football is moving" back that way. Mississippi State defensive coordinator Manny Diaz, who has attempted to gameplan against Fournette and Henry this season, has a simpler explanation. "There's nothing I can think of big-picture wise," he said. "Just a run of some really talented guys with unusual size and speed. I think Fournette and Henry would be freaky no matter what era they played in."

Fournette and Henry are cut from the same freaky archetype and had have rare blends of size and speed. Henry is 6' 3" and 242 pounds yet could be seen sprinting away from Mississippi State defensive backs on touchdown runs of 74 and 65 yards on Saturday. Fournette is also uniquely nimble for a 6' 1" 230-pound tailback, as he can push a pile and run over or around opposing linebackers.

Elliott checks in at 6-feet and 225 pounds, meaning he's not quite as big as Fournette and Henry. But he's powerful, as evidenced by his highlight reel of blocking players off the ball. What separates Elliott is his blended talent, as he excels at pass protecting and catching the ball from the backfield. He also can run between the tackles as efficiently as he can dance around the edge.

Cook may be the least heralded of the group, but he's averaging 8.1 yards per carry and is second nationally with 152.1 yards per game. McCaffrey, who is 6-feet and 201 pounds, may have the most pure explosion out of all the top backs. He leads the nation in all-purpose yards (241.8) by a country mile thanks to his special teams versatility (San Jose State's Tyler Ervin is No. 2 at 209.8).

So why the gaudy running back numbers? One theory an NFL scout offered makes some sense. He pointed to the cyclical nature of football as defenses have become so prepared to stop spread offenses by becoming more nimble and versatile that they aren't as equipped to stuff the box and slow the run game. "There's been such a priority placed on the edge and stopping the spread that teams are susceptible to the run game," the scout said.

While that evolution is certainly true, it's doesn't fit for this elite tailback crew. Four of the five play in smashmouth pro-style offenses, with Ohio State's Elliiott the exception. "There's no shift that I can feel," says Buckeyes defensive coordinator Chris Ash, speaking generally of the trend. "Other than it just happens to be a season with some talented running backs on teams that might not have an elite quarterback and have to run the ball more."

That observation rings particularly true for Alabama, LSU and Florida State, none of which have been able to rely on a consistent downfield passing game this season. Instead they have pounded the ball with their dominant backs. "Those guys are special players," says Clemson defensive coordinator Brent Venables. "Anytime you have an Adrian Peterson-type of guy, you'd be a fool as a coach not to feature him. I think that's first and foremost. Even though it's a spread game and those types of things, the most successful teams, year in and year out, run the ball. You get race horse like that, you ride it."

Next year may be a better barometer whether this season of tailback dominance is an anomaly or a trend. But here's an early indicator that Bielema's prediction could be correct—Fournette, McCaffrey and Cook are all just sophomores. They'll be among the early favorites to win the 2016 Heisman Trophy, meaning this run on dominant running backs could continue next season.