The age of the two-way player is back in college football. Almost.

Players like Ole Miss’ Robert Nkemdiche, USC’s Adoree Jackson and UCLA’s Myles Jack (prior to his season-ending injury) are among the leaders in a new wave of athletes who play on offense and defense, something college football has lacked since the 1940s.

For a long time in the early years of the sport, players saw action on both sides of the line of scrimmage due to a rule limiting the number of substitutions. Legends like Bronko Nagurski and Jim Thorpe dominated multiple facets of the game; but as football evolved, its players began sticking to one side of the field as rules changed.

As the years progressed, fewer and fewer two-way players made headlines, as coaches prefered to maximize athletes’ skillsets on only one side of the ball. Sure, the Dick Butkuses and Charles Woodsons of the world popped up every now and then, but until recently, if a player came out of high school as a defensive lineman, he’d stay a defensive lineman in college.

But in the past two years, a resurgence of the Old Way, or Ironman Football, has returned, albeit in a limited way. So far in 2015, Nkemdiche -- a defensive lineman -- has scored three times (two rushing touchdowns and one receiving touchdown) on four offensive touches. Jackson -- a defensive back -- had three receiving touchdowns on 10 catches as a freshman in 2014 and has one touchdown on seven catches in 2015.

Though they play two sides of the ball, neither player’s time on offense and defense are split 50-50. In the case of Nkemdiche and Jackson, their primary focus is on defense, where they were recruited to play.

Nkemdiche, now a junior, dominated as a tailback in high school but didn’t see time on offense until this year in college.

“We decided in fall camp this year we would have a small package for him and we spend about maybe five minutes on Wednesday and Thursday with him and [fellow defensive lineman] DJ Jones just learning the package for that week,” Ole Miss coach Hugh Freeze said. “We’ve always known he could do it, this year we just decided to make sure we had that prepared in games.”

Nkemdiche has made the most of his touches, though, scoring on a 31-yard catch in the first game of the season and then twice on runs from the goal line in two of the next three games for the Rebels.

“Typically his possessions on offense are one or two plays max,” Freeze added. “His priority is defense so we’ll always lean towards that.”

Jackson is an even more interesting specimen. Much like Michigan used cornerback Charles Woodson in the late 1990s, USC’s Jackson sees time mostly as defensive back but also returns kickoffs and punts and plays receiver in some packages for the Trojans.

The electrifying speed and shifty playmaking ability of Jackson makes him a threat every time he touches the ball, which is primarily why Trojan coach Steve Sarkisian gets him as many opportunities to make plays as possible.

“The majority of his time is spent on defense.” Sarkisian said. “We’re very selective with what we do with him offensively, but when we have him offensively, we try to be on point with him. He’s not just out there running plays, it’s for a reason. I think that’s why the end result has been so good when he gets his chances.”

While Jackson hasn’t scored on special teams through the first four games of the year, the sophomore did accrue 184 all-purpose yards in the Trojans’ Week 4 win over Arizona State, including an 80-yard touchdown on a short pass from quarterback Cody Kessler and a 45-yard reception to set up another touchdown.

“He’s a heck of a player with the ball in his hands,” Sarkisian said, “so it’s just trying to find ways to be creative to get him the ball and allow him to go do his thing.”

Among the 20 players who’ve seen action on both sides of the ball for major programs in the past two years, particular positions on defense tend to line up perfectly with positions on offense. Nkemdiche, for example, excels as a bruising goal line fullback with a 6-foot-4-inch, 296-pound frame, while the 5-foot-11-inch, 185 pound Jackson fits the mold of a typical wide receiver.

The pattern extends past Nkemdiche and Jackson. UCLA’s Jack is a rusher at 6-foot-1-inches and 245 pounds, while Oregon’s Charles Nelson plays wide receiver and defensive back at 5-foot-8-inches and 170 pounds. Florida’s Vernon Hargreaves III is a cornerback who sees time at wide receiver, while 275-pound Cody Grice -- a defensive lineman at Akron -- has three touchdowns on six carries for eight yards.

Certain positions convert well to other positions because of body type and skillset, according to Gordie Lockbaum, a standout tailback, defensive back and special teams return man at Holy Cross in the mid 1980s.

“Athletically, they’re going to fit in the role they need you. You’re not going to put a 6-foot-4, 300-pound tackle out at wide receiver,” he said. “And when you talk about receivers, you need somebody with wheels, somebody that’s going to be able to run. If you’re a cornerback in the college level, you know you can run. It’s a body type that suits itself to each side.”

Even more so, when a linebacker or defensive end lines up as a running back or fullback, he already understands how to beat blitzs or exploit block gaps, while defensive backs know how to read coverages as a wide receiver.

“It’s a skill set,” Lockbaum said. “Whether it’s about speed or size, there are positions that translate well."

The resurgence of these athletes, Lockbaum said, can be traced to two different schools of thought: the maximization of a player’s talent and to find any competitive edge against an opponent.

“I think a coach would be foolish not to look at his entire roster and know that he could plug somebody in for a certain number of plays,” Lockbaum said. “You don’t have to teach them the entire offense, just exploit the amazing talent the kid has and ask him to do a couple of things.

“And if you’re doing it, others teams have to prepare for it. They have to waste practice time, waste film time talking about somebody that might only be in the game a couple of plays, which is always a good thing for anybody from a strategic standpoint. It’s a great distraction.”

There are problems that exist with overusing athletes, though, and Lockbaum experienced the plight of the two-way player firsthand. During a game against Army in 1986, the same year he finished fifth in the Heisman Trophy balloting, Lockbaum played 143 of 171 snaps. That overexposure can lead to injury, which runs the risk of weakening the team on both sides of the ball.

“If you have somebody that played both ways full time, and they got hurt, you just lost two positions,” Lockbaum said.  “The more you use him, the more you risk losing him at his primary position.”

The injury risks, coupled with the overabundance of players on any given sideline, is why two-way athletes won’t become the norm in college football. But with so many coaches looking at new ways to win games, players like Nkemdiche, Jackson, Jack and a score of other athletes are continuing to take on bigger and bigger roles on offense and special teams.

“The other things is the motivation side,” Lockbaum said. “If you’re a defensive guy -- and these are very special athletes that probably played both ways in high school -- they miss it. They miss the chances to put their hands on the ball and get on the field on the offensive side. They’re hungry, really hungry to make something happen. They’re not going to take a play off, they’re going to give it their all. These kids are competitive. When they’re out there on offense, especially with guys they don’t practice with, they practice against, they want to show that they’re going to get it done.”

Here are the rest of top two-way athletes in college football: