I absolutely love the career of Jarryd Hayne so far. A 2015 National Football League rookie, Hayne is actually a superstar in a different kind of football: rugby football. In his native Australia, this massive 6-foot-2, 220-pound running back and kick returner immigrated to the United States this offseason and is already helping as a change-of-pace thumper and return specialist for the San Francisco 49ers.

Despite the rules shifts he’s had to figure out in his transition, it’s seemed fairly smooth for the massive runner, and he’s even joking and goofing around in his spare time on the field, as heard when he was mic’d up last week against the Green Bay Packers.

I know learning English is hard, but all he had to do was learn American; easy as apple pie.

Although Hayne’s career hasn’t made him an instant NFL superstar, he’s become a solid contributor after coming out of relative obscurity on this side of the world. He’s a solid player who’s plying his trade in our favorite league, and we should at least take account of players like him who go from little-known to the big time; we might find someone particularly special sooner or later.

That’s why we ourselves have to scour the globe and track down the best answers to this question: which unheralded rookie running backs in the NFL are impressing already in their careers?

David Johnson, Arizona Cardinals

He’s more widely-known now than he was on Day Two of the 2015 NFL Draft, but former University of Northern Iowa running back David Johnson is actually still less-appreciated than he should be. For your reference, Johnson was the top running back at this year’s NFL Combine in the 40-yard dash, the bench press, the vertical jump, the broad jump, and the three-cone drill; all of that was done with an imposing 6-foot-1, 224-pound stature.

The problem is: head coach Bruce Arians has been actively trying to limit the rookie’s touches, suggesting that he’s still too raw. Arians has highlighted veteran Chris Johnson in starter Andre Ellington's injury-induced absence.

Our  Karlos Williams nonetheless was a force on the football field in college. Fascinatingly, he was a safety for the first two years of his college career but converted to running back the year Florida State won the BCS Championship. Coincidence? I think not.Karlos Williams, Buffalo Bills

He brings the kind of hard-nosed effort expected of a safety to how he plays running back, which made him a perfect fit for Buffalo Bills’ head coach Rex Ryan’s “ground-and-pound” offensive philosophy. With LeSean McCoy dealing with a myriad of injuries this year, Williams has filled in admirably, rushing 29 times for 226 yards (7.8 yards per carry) and 3 touchdowns.

He’s looked even better via our metrics, ranking an impressive ninth in Total NEP on just 49 offensive opportunities. His strength is his ground work: he ranks second among running backs with at least 20 attempts in per-play Rushing NEP. Though currently in the NFL’s concussion protocol, he should be strong when he returns.

Duke Johnson, Cleveland Browns

Another Day Two runner from this year’s draft, Duke Johnson of the Cleveland Browns was hailed by some as a three-down back and a franchise-type player that a team could build an offense around. He showed that kind of potential at Miami, as he tops their record book for rushing yards in school history -- despite leaving for the NFL Draft after his junior season and breaking his ankle midway through his sophomore year.

This speed demon from “The U” oozes NFL potential but hasn’t been able to showcase all of it yet. Caught in a timeshare with starter Isaiah Crowell and lagging due to preseason hamstring and concussion issues, Johnson has taken some time to get up to speed in the running game. He ranks 50th in Rushing NEP among backs with 20 or more opportunities so far. His receiving skills have remained intact, however, and he is one of the best pass-catchers out of the backfield already.

He ranks 14th among running backs in Reception NEP, as well as a sparkling 7th in Target NEP. If he can improve his rushing, he will be an NFL force.

Terron Ward, Atlanta Falcons

We’re going deep with undrafted rookie Terron Ward of the Atlanta Falcons, who accumulated 20 of his 21 opportunities on the season last week against the Houston Texans. Why am I so pumped about a 5-foot-7 undrafted running back out of Oregon State?

Opportunity, my friends. That’s the magic word. He may have just 21 opportunities thus far into the 2015 season, but with Falcons’ rookie Tevin Coleman ailing and new starter Devonta Freeman taking on a huge workload, Ward saw nearly a starter’s load in a change-of-pace and fourth quarter relief role in Week 4.

On that serving size, he racked up a Total NEP that already puts him 26th among running backs with at least 20 opportunities. He’s not overly athletic, but he’s finding ways to leave his impact on the league, and the results are undeniable. In a high-powered Atlanta offense, he could be in for plenty of cleanup duty this year. He’s an interesting player to watch going forward.