NFL veterans and rookies have their offseason training activities, and so do fantasy football owners. Granted, fantasy OTAs aren’t nearly as physically strenuous as pounding your shoulders into a tackling sled.

Instead, fantasy involves loads of research and it’s never too early, even with the 2016 season four months away, to take a look at draft boards and find some of the hidden gems capable of bolstering your roster. Especially rookies.

This year, 20 running backs were selected in the 2016 NFL Draft and we’ve identified five that could make a major impact in the upcoming season.

Rookie running backs often fall into two categories in their first NFL season. Either they are a high draft pick with huge expectations, or they’re forced to battle for a roster spot first before any talk of actual playing time. Last year’s best example of the former was the St. Louis Rams' Todd Gurley, who went No. 10 overall, and responded by ranking third in the league with 1,106 yards and 10 touchdowns.

Then there was the Seattle Seahawks’ Thomas Rawls, who went undrafted and wound up playing in 13 games (starting seven) while helping Seattle overcome the loss of injured Marshawn Lynch. Rawls became a fantasy sensation with 830 rushing yards and four scores.

Most of the running backs on our list will probably have to wait before they see meaningful playing time, let alone make an immediate impact in owners’ lineups. But researching them now should pay dividends while less studious owners sleep on their potential.

Ezekiel Elliott, Dallas Cowboys

The difference between DeMarco Murray in 2014 and the Cowboys' running game in 2015 turned out to be quite noticeable, with Murray rushing for 1,845 yards in a free-agent contract year, while the Cowboys' entire running game combined for 1,890 yards in 2015. With Elliott now in the fold, there is understandable optimism growing in East Texas.

The hype machine has been working full-blast in Cowboy nation and fantasy football circles since the night of the draft, in part due to Elliott’s back-to-back 1,800-plus yard seasons with 41 touchdowns at Ohio State.

Elliott’s likely to garner first and second-round consideration from fantasy owners in all league formats, in particular dynasty leagues, and there isn't much reason to doubt he will at least have a solid rookie campaign. But expectations should still be tempered.

Dallas’ o-line is intact, Tony Romo’s recovering well from surgery, Dez Bryant should be back to top form, and all the while Elliott may have to lobby for carries against a rather deep rushing unit. Darren McFadden’s back, Dallas added Alfred Morris from Washington, and Lance Dunbar caught 21 of 23 targets. Expect an intense running back competition during training camp, and keep a close eye on the victor before you draft.

Derrick Henry, Tennessee Titans

The Titans ranked No. 25 in rushing yardage last season with four backs earning starts and Antonio Andrews leading the way with 520 yards and three scores at a 3.6-yards-per-carry clip. Injuries, a rookie quarterback, and a suspect offensive line surrendering a league-worst 54 sacks were all culprits.

Tennessee didn’t really address the o-line problem in free agency, with center Ben Jones and right tackle Byron Bell signed for a grand total of $19.75 million. The Titans instead spent the No. 8 pick on Michigan State lineman Jack Conklin and in the second round picked up Heisman Trophy winner Henry.

A bruising, punishing back at Alabama, Henry already has the size to crush linebackers and defensive backs if he breaks out into the open field. Tennessee traded for Murray, who will undoubtedly get plenty of carries, but Henry can be quite useful in short-yardage situations and even at the goal line.  Henry could be a solid No. 2 for the Titans almost immediately, particularly if he outworks Antonio Andrews and if Murray struggles. In standard 12-team leagues Henry’s likely to go undrafted, so as a free-agent pick-up after your draft he’s worth a shot as the season wears on.

Devontae Booker, Denver Broncos

Yes, Booker has a ton of work ahead of him. He’s currently one of six running backs on the defending Super Bowl champion’s roster, including last year’s leading rushers in Ronnie Hillman and C.J. Anderson. There’s also the matter of how well or how quickly the new starting quarterback assimilates with the offense, which plummeted from No. 2 in the league with 30.1 points per game in 2014 to No. 19 with 22.2 a contest last year as Peyton Manning dwindled away and the defense won most of the games.

Denver was also No. 17 in rushing in 2015, but it stole left tackle Russell Okung from Seattle and Donald Stephenson from Kansas City while also adding a workhorse like Booker to keep Hillman and Anderson on their toes.

Booker’s a dual threat who gained 3,395 yards and 23 touchdowns from scrimmage over only two seasons in Utah, and he may just need a chance to prove himself. Like Henry, Booker probably won’t get selected in drafts unless you’re in a very deep dynasty league. He’s worth a flier and is a back to watch as training camp and the season unfolds.

GettyImages-499071610 Former UCLA running back Paul Perkins could earn playing time as the Giants try to rediscover their ground game. Photo: Getty Images

Paul Perkins, New York Giants

Eight backs went ahead of Perkins in the draft due to most scouts panning his lack of size even though they admitted he has incredible moves in the open field. But that allowed New York to snag him in the fifth round. The Giants haven't had a 1,000-yard rusher since 2012, which was also the last time they cracked the top-half of the league in rushing.

That essentially means the Giants haven’t had a true No. 1 running back since Ahmad Bradshaw, even though Rashad Jennings started all 16 games and Shane Vereen caught 59 balls out of the backfield. It wouldn't be surprising to see new head coach Ben McAdoo mix things up a little more in 2016 and run the ball a bit more. 

Perkins, who scored 23 touchdowns in 26 games his last two seasons with UCLA and averaged 5.6 yards per carry in college, will have to beat out Andre Williams for even a decent shot at touches but a chance could present itself at some point in 2016. He is an under-the-radar talent, and it wouldn't be surprising if he plays an important role for New York in a wide open NFC East.

Kenyan Drake, Miami Dolphins

A gifted back who fell to the third round because of a poor injury history, Drake finds himself in a very intriguing situation in Miami. The Dolphins let 2015’s leading rusher Lamar Miller walk in free agency, so Drake will be competing against Jay Ajayi and Damien Williams in training camp.

With Miller starting all 16 games last year and a broken rib suffered in the preseason, then-rookie Ajayi didn’t get a chance to prove himself. Meanwhile, in two years Williams has totaled just 181 rushing yards and averaged 3.5 yards per attempt.

Since Ajayi and Williams have yet to truly stand out, the No.1 running back slot is wide open. Drake can make a name for himself in camp, and perhaps even become the featured rusher. He’ll be most effective as a pass-catching back and potentially a returner. With rookie lineman Laremy Tunsil paired beside Branden Albert on the left side, Drake, or any of Miami’s backs, has the potential to explode in 2016.