Samaje Perine will take over as Washington’s featured running back after injuries to Robert Kelley and Chris Thompson. (Jonathan Newton/The Washington Post)

One by one, they have disappeared from the Washington Redskins’ roster the past four months — Keith Marshall, Matt Jones, Mack Brown, Rob Kelley and Chris Thompson — amounting to a case study in why running backs have the shortest NFL careers.

They’re battered virtually each time they touch the ball or block for a teammate. And whether casualties of season-ending injury, poor performance or a business-driven roster move, they’re often viewed as easily replaced.

Now comes rookie Samaje Perine — a 5-foot-11, 236-pound bulldozer of a back with a running style described by an unidentified NFL scout in his pre-draft profile as “all bully with very little ballerina” — who may prove sturdier stuff.

Perine was anointed the Redskins’ lead running back after Kelley’s season ended with knee and ankle injuries. Perine showed a veteran’s patience and grit in Sunday’s overtime loss at New Orleans, rushing for 117 yards (the first Redskins back to break 100 since Kelley in Week 11 last year against Green Bay) and recording his first touchdown on the ground.

On Thursday night against the New York Giants, the pressure on Perine will get more intense. With Thompson joining Kelley on injured reserve after breaking his right leg against New Orleans, Perine is now the most experienced back in Coach Jay Gruden’s offense.

Ahead of the draft, one scout described Perine as “all bully with very little ballerina.” (Toni L. Sandys/The Washington Post)

That’s a tremendous weight for an athlete who turned 22 in September. But since childhood, Perine has had the manner and maturity of someone much older.

“I get that a lot,” Perine said this week, breaking into a broad smile and offering a low-pitched chuckle.

As his mother, Gloria, explains, Samaje was an only child, reared largely by his grandparents in Jackson, Ala. She was young when she gave birth, and her parents urged her to finish school and not give up her college plans, insisting they take care of their grandson until she was established. Today, she credits Samaje’s old-school persona to his beloved grandfather, Sam, after whom he patterned himself.

“My dad is a just a hard-working man who really loves family and always did what he could for all six of us kids,” Gloria Perine said.

Samaje was always big for his age, thick and stocky to the point that no one believed he was just 8 years old when Gloria Perine signed him up for Pop Warner football in Texas after she had earned her degree and Samaje had come to live with her.

At 11, he decided he wanted to get bigger still, so he asked for a set of dumbbells. And rather than ask his mother for a heavier set when he could handle those, he taped bricks to the barbells to add weight.

Perine added track to his regimen at Hendrickson High in suburban Austin, where football players were required to play a second sport in the offseason to stay in shape year-round. He ran sprints, competed in the triple jump and long jump and was part of a relay team, finding a crossover benefit in mastering the baton handoffs it required.

As a freshman at Oklahoma in 2014, he set a Football Bowl Subdivision record by rushing for 427 yards (and five touchdowns) in a 44-7 rout of Kansas. Solitary by nature, he shied from the spotlight and, when pressed about the feat, raved about the Sooners’ offensive line. It earned him the nickname “Humble Beast” in a SoonerSports.com profile by John Rohde, who wrote that the freshman had such an adult comportment that he had been mistaken for a recruit’s father when he first appeared on campus.

What made Perine special at Oklahoma, where in three seasons he set the school’s career rushing record (4,122 yards) and completed all but eight credit hours toward his degree in human relations (he has enrolled in classes to complete it in the spring), was largely what attracted the Redskins to him once he entered the 2017 draft: a low center of gravity, balance to stay upright after initial contact and production despite being paired with standout Joe Mixon.

When Redskins scouts called Oklahoma director of sports enhancement Jerry Schmidt, who serves as strength coach for the football team, he raved about Perine’s maturity. Yes, his strength was shocking: He bench-pressed 440 pounds — a typical back might lift 350 — and squatted 540. But Perine always wanted to get better, he told them, and had a pro’s seriousness about his diet and year-round fitness.

“He understands how important it is to be strong at the end of the year,” Schmidt said in a telephone interview. “The way he takes care of himself and trains, as other people start to get weaker, he’s going to get faster and be able to play a high level at the end of the season. . . . That’s what I told the Redskins: ‘He’s going to change your locker room because he’s always looking to get better. He’s always positive. And he’s the same guy every day.’ That’s who he was at 17, and that’s who he is.”

Perine had no idea he was on the Redskins’ radar until they chose him in the fourth round, but he soon realized his good fortune, he said, after being welcomed by teammates who spared him the rough treatment and cold shoulder that many NFL rookies receive.

That didn’t make his preseason debut any easier. Unaccustomed to running from formations with the quarterback under center — as opposed to the shotgun, where the back can see far more — he fumbled once and dropped a pass against Baltimore.

Ball security is Gruden’s top priority for backs; blocking is No. 2. And the coach wanted to be sure Perine could handle both before relying on him. Perine understood, so he didn’t flinch when he was limited to special-teams duty for a stretch.

Kelley and Thompson “were the guys and have more experience than I do in the offense,” Perine explained. “As long as I was helping the team in some way, special teams, I was good with it.”

With the Redskins (4-6) winless against NFC East opponents heading into Thursday’s game against the Giants (2-8), Perine will be asked to help in a more significant way.

Asked this week whether Perine had earned his trust, Gruden cracked: “Well, Kirk [Cousins] threw an interception, too, one time, and I still trust him. We can’t just bash these players because they have a turnover or make a mistake; otherwise, we wouldn’t have any players or coaches left. I think you just learn from your mistakes. . . . I don’t think it is an issue right now.”

Every NFL player, however patient, wants to be “the guy” at his position. Perine regrets the circumstances, voicing remorse over the loss of Kelley and now Thompson, who was ferried off the Superdome field on a cart Sunday, his shattered leg in an air cast.

“Now it’s just me from the original group,” he mused. “It’s tough — especially for a guy like C.T. He’s a hard-working, loving guy who never wants to hurt anyone, never wants to do wrong by anyone. Just to see him go down like that, with the kind of season he was having, it was really tough.”

Perine had wanted to win the game for Thompson, and he did his best. But after exceeding 100 yards, he slammed into an immovable force when two Saints defenders broke free on a third-and-one run with just over two minutes remaining. A first down would have sealed a victory for Washington, and the play has been second-guessed since.

“They had some very unorthodox things they did on defense,” Perine said. “We just got mixed up. They just came free. At that point, I did what I could, but it wasn’t quite enough.”

Nearly 150 relatives and friends made the three-hour drive from Alabama to New Orleans for the game. Although Gloria Perine hasn’t missed a Redskins home game this season, she will be with her parents and relatives in Alabama this Thanksgiving and will watch the Redskins-Giants game on TV.

She will give thanks for her life’s many blessings and for Samaje’s health. She has begged him over the years, to no avail, to run out of bounds when the game gets ugly. “Can you not?” she will ask.

Each time, her son replies, “Mom, it’s the way I play. I’m physical.”