LINCOLN, Neb. -- His late grandfather's United States Marine Corps ring hangs from the mirror of Zack Darlington's F-150 XLT SuperCrew pickup truck, alongside the dog tags left over from high school football, adorned with a call to exhibit honor, excellence and effort.

No more appropriate representation of Darlington could exist.

When the Nebraska quarterback-turned-receiver and placeholder announced Jan. 30 that he would forgo his final season of eligibility to join the U.S. Army, his 189-word post on social media told only a fraction of the story.

I'd like to say thank you for everything, I'll always be a Husker! #GBR4EVER pic.twitter.com/0GiruLF7Sw — Zeus (@DarlingtonZack) January 30, 2018

Darlington endured a litany of injuries that predate his stardom at Apopka High School outside of Orlando, Florida. Once he was healthy, he experienced great victories that culminated in a state championship five years ago, but disappointment at Nebraska, failure and grief followed. Then came the renewal and new passions.

All of it shaped him into a 22-year-old with a clear vision to serve in the U.S. Army Special Forces and build a life in rural Nebraska. He said he planned to reach his goals with teamwork, toughness, leadership and selflessness -- virtues carved into his being that are evident from merely brief encounters with the second oldest of Rick and Shelly Darlington's seven children.

"I could never be more proud to be his brother," said Jackson Darlington, a sophomore football standout at Apopka High. "Just the thought that he's willing to sacrifice his life, everything that he does to protect us that brings me so much pride. I just feel like he's meant for this.

"He cares a lot more about other people than he does himself."

MANY YEARS AGO, Ty Darlington thought his brother Zack was soft. A lineman en route to All-Big 12 honors as a center at Oklahoma -- where he now serves as a quality-control assistant coach -- Ty is two years older than Zack, who played quarterback.

The Darlingtons lived on a lake near Umatilla, Florida, 25 miles north of Apopka. Rick and Shelly, both educators, home-schooled their children until eighth grade, and the kids spent nearly all of their free time outside.

If Ty tackled Zack, the younger brother often ran inside and complained to their mother. Ty's perception on the matter changed about eight years ago.

In an important youth football game, one swift kick to the face from a defender knocked the top front teeth from Zack's mouth. The bloody quarterback climbed to his feet and tossed his teeth to the sideline. They sat in a cup of milk for the remainder of the game as Zack led his team to a score, then clinched victory with a series of sacks as a defensive end.

"That was the first time I ever thought, 'Wow, this kid has something special in him,'" Ty said

Fake front teeth and all, Zack's toughness persisted. As a sophomore and first-year starter for Apopka coach Rick Darlington, Zack suffered a torn labrum in his non-throwing arm. His shoulder popped from its socket several times in a single game, but he continued to play, biting down hard on a towel to suppress his desire to scream when medical staff intervened.

The next year, he fractured the wrist of his throwing arm with several games left in the season but played while wearing a splint and led Apopka to an 8A state championship with a 53-50 win at the Florida Citrus Bowl.

And then there was the time, driving home from practice in Ty's senior year, that the brothers saw an elderly man struggling in a lake after his boat capsized. Before Ty parked the car, Zack had dived from the dock. He flipped the boat and pulled the man to safety.

"That's just normal instinct for him," Ty said. "He's an incredible leader, especially in tough moments. He loved football not because of the X's and O's; he loved football because of the toughness, the leadership opportunities, the brotherhood. Those are all things that the military has to offer.

"When you look at it like that, it's not any wonder this is what he has chosen."

Zack Darlington hangs his late grandfather's United States Marine Corps ring and dog tags from high school football from the mirror of his truck. Mitch Sherman/ESPN

BEFORE PLANS FOR THE MILITARY, there was Nebraska. Darlington enrolled in spring 2014 and immediately met Sam Foltz, a walk-on punter who took the young quarterback under his wing.

"He could kick the ball," Darlington said last week, "but that dude was so much more than a punter."

Darlington rose to prominence under new coach Mike Riley with a strong showing in the 2015 spring game, but he remained buried on the quarterback depth chart and did not appear in a game that fall.

Still Darlington prided himself as a jack of all trades and remembered a coin given to him by an Apopka assistant coach after the 2011 game in which his shoulder repeatedly popped free.

The coin pictured a Jack and represented team over self. Darlington treasured it. And when he left for college in 2014, he gave the coin to his brother Jackson, promising to carry the same traits to Nebraska.

"In high school, I got to be the star," Darlington said, "so I didn't have to worry about giving up any dreams for the team to succeed. But when I got to college and this disappointment happened, it was a moment of character and test -- 'You say you're about this. Are you really?'

"So that was my thing: 'Whatever it is, I'll do it.'"

He threw himself into weightlifting, often working out twice a day. It earned him the respect of teammates beyond his close friends, who included roommate and place-kicker Drew Brown. Darlington ascended to a leadership position. He carried the American flag from the tunnel before every game in 2015.

And in spring 2016, when the coaches asked him to play receiver, he embraced the new role.

"Rather than sit back and mope and complain or leave," he said, "you've got a find a way."

In July 2016, Foltz, a first-team All-Big Ten punter, died in a car accident. It devastated the Cornhuskers. Few were closer to Foltz than the kicker Brown, Darlington's roommate. To serve Brown, Darlington took Foltz's spot as the holder.

"He didn't have dreams of being the holder," Ty Darlington said. "But that's what the team needed him to do."

Brown needed him most.

"I needed Drew to know that he had a guy who wanted to be in that position," Zack Darlington said, motivated in part by Foltz's kindness toward him that first spring. "He needed someone who loved him like a brother."

In the 2016 opener against Fresno State, memorable for the Huskers' haunting formation on the first punt, during which they lined up without a punter, there was another meaningful moment. Early in the fourth quarter, Nebraska called for a two-point conversion out of a swinging-gate look.

Darlington scored on the play originally designed for Foltz. He scored in Foltz's honor.

He did more for Foltz, too, speaking at an event early in 2017 to support the Sam Foltz Foundation. In attendance that day was Kenny Winn.

"Just a chance encounter," Winn said.

After graduating from Nebraska in the spring, Zack Darlington plans to follow in the footsteps of his grandfather, whose Marine Corps ring Darlington keeps in his truck, into the military. Mitch Sherman/ESPN

WINN'S RÉSUMÉ reads like something from a Tom Clancy novel.

He enlisted in the Marines out of high school in Fremont, Nebraska, in 1994. Winn served four years as an infantry rifleman.

"Traveling around the world, floating on a ship, waiting to kick someone's ass," Winn said. "That's what Marines do."

He returned to Nebraska and served full time in the Nebraska Army National Guard, working with the 134th Long Range Surveillance Detachment. Winn performed airborne work and reconnaissance as a platoon leader and first sergeant during tours in Iraq, Bosnia and Afghanistan.

He teamed with federal law enforcement agencies as the counterdrug coordinator for the Nebraska National Guard and recently retired as a command sergeant major.

In retirement, Winn co-founded TIII Operational Solutions, a tactical training and security consulting company.

While speaking for the Foltz Foundation, Darlington caught Winn's attention, and he introduced himself. They set up a few meetings. Darlington participated in several shooting exercises. And when they began to grow close, Darlington confided in Winn that he had always wanted to join the military.

"There's a lot of people who say things like that," Winn said. "But you could tell he honestly meant it."

Winn tried early to talk Darlington out of it. He offered several career options.

"Zack turned up his nose at a lot of things, simply because he wants on a specific career path, which is the infantry," Winn said. "We're very like-minded people. I just think it's funny how people like that gravitate to each other."

Darlington has begun the enlistment process. He plans to head to basic training in Fort Benning, Georgia, after graduating from Nebraska this spring. At his age, Darlington wants to take a fast track and get airborne certified before vying for positions at sniper school and Army Ranger school.

Darlington said he understood the work necessary to achieve his goals. His experience in football will no doubt serve him well in the military and beyond, he said.

Teamwork, toughness, leadership and selflessness.

"I don't think many people even recognize what selflessness is anymore," Winn said. "Zack is like the encyclopedia version of it."

On the cusp of this life change, Darlington appeared at peace on a cold February morning in downtown Lincoln, sitting behind the wheel of his pickup as he cradled in his hands the ring that belonged to Dave Darlington, Zack's grandfather who fought in World War II.

"I feel like someone has to go and do this," he said. "Someone has to go and serve. If anything, I trust my skills and instincts and the way that I operate over someone else. That's just how I am.

"In a football game, when it's fourth-and-goal, are you going to pick to give it to someone else? Hell, no. Give it to me."