It happened, to the recollection of Khalil Mack, at a gas station along U.S. 1 near his home in Fort Pierce, Florida.

Sandy Mack, Khalil’s father, spied a friend and colleague from the jail house where he worked.

“His name was Hucklebuck, and he was a big dude. My dad was a big dude,” Khalil said following a training camp practice. “My dad was always telling people how many push-ups I could do, and Hucklebuck wanted to see. He said, ‘I’ll bet he can’t do 20.’

“My dad says, ‘OK, Khalil, go ahead.’ So there I was — outside on the concrete at a gas station, maybe 7 years old. And I pumped out 60 push-ups.”

Khalil’s dad is hazy on the gas station exhibition, but has no doubt it’s true — because such demonstrations were relatively commonplace.

“People didn’t believe me when I said he could do push-ups — and I mean straight up, military-style push-ups,” Sandy Sr. said. “No slouching — I don’t go for that. People would hear about it, they’d ask me and I’d say, ‘Khalil, show ’em.’ And he’d bounce ’em out like nothing.”

Going into his third NFL season, the push-up prodigy is all grown up, a bona fide star at age 25.

Mack is on anyone’s short-list of the NFL’s top defensive players, along with Houston defensive end J.J. Watt, Denver linebacker Von Miller and Los Angeles Rams defensive tackle Aaron Donald. He was named All-Pro at two different positions — defensive end and linebacker — and his 15 sacks included a five-sack explosion in an upset win over the eventual Super Bowl champion Broncos.

Within a year or two, general manager Reggie McKenzie will present Mack with a contract that is expected to make him the first defensive player in NFL history to average $20 million a season.

None of which Mack is comfortable discussing. Quarterback Derek Carr, the offensive cornerstone of the franchise and also in line for a major payday in the near future, uses humor to disarm teammates who joke about his impending wealth and stardom.

“I try and laugh it off because I’m not smart enough to not say anything,” Carr said. “He just deflects it.”

Mack’s strategy is to give no discernable reaction. Without fuel, the fire will cease.

“He ignores every bit of it,” fullback Marcel Reece said. “He just looks straight ahead.”

In contrast to Watt, a cottage industry when it comes to commercials, media time and branding, Mack, according to his older brother, has turned down commercial opportunities as well as a guest appearance on HBO’s “Ballers” starring Dwayne “The Rock” Johnson.

“He wants to be known as the best before he gets endorsements, and he doesn’t feel like he’s done anything yet,” Sandy Jr. said.

Ask Mack about the pot of gold that awaits and he recoils like an adolescent being asked about his first girlfriend.

“I’m not comfortable talking about that stuff. That’s just not me,” Mack said. “I like to grind and not think too much about the good stuff. I like to focus on the stuff I need to get better at.”

Toward that end, Mack agreed to pull out a laptop computer to give a mini-clinic to his interviewer. He did so on one condition: No game clips of him making sacks or tackles for losses. Mack would only show the plays where he made a mistake.

Out of a file labeled “KHALIL BAD,” Mack cues up a play from last Nov. 15, a 30-14 loss to the Minnesota Vikings in Oakland.

Minnesota quarterback Teddy Bridgewater fakes a handoff to Adrian Peterson and rolls to his right.

Mack hesitates when confronted with right tackle T.J. Clemmings and tight end Kyle Rudolph, and Bridgewater rolls free to the right. The pass is completed for a short gain along the sideline.

“I could have gotten to the mesh point right there, the quarterback and running back exchange,” Mack said. “My angle was bad, and I played it too flat. I could have made it a lot easier for our cornerback David Amerson out there on the edge.”

Mack runs the same play back and forth, shaking his head slightly.

“I’m looking at my footwork, hand placement, I’m thinking about all those things,” Mack said. “I know the next team will go right to this play to see the stuff you don’t do too well.”

Next, Mack slices inside the guard and tackle and has a clear shot at Bridgewater. One problem: He takes a swipe at the ball, and Bridgewater gets away.

“These are the ones you have nightmares about right here,” Mack said. “I had the sack, and I let it go. You’ve got to make those, man. I was trying to reach for the ball instead of tackling. That could have been 16 sacks.”

Another play, another split-second hesitation, another chance for Mack to self-correct.

“See, this is nasty right here,” Mack said as Peterson takes a handoff for a short gain. “I thought it was going to be a play-action pass, and I waited instead of just blowing him up.”

It goes on like this for a few more plays before he closes the laptop and ends the lesson. Mack has made his point. He could have been better. Should have been better. Much better.

“That would have been 17 sacks … 18 …,” Mack said. “When you’ve got a chance, you’ve got to capitalize.”

Khalil Mack arrived in a big way on Feb. 22, 1991, the second of three sons to Sandy and Yolanda Mack.

“He was 10 pounds, 8 ounces, and they thought he might be diabetic because he was such a big baby,” Yolanda said. “But he was just a healthy baby. There was no fat on him anywhere. He already had a muscular frame — he had muscles on his calves.”

As his older brother Sandy Jr. said, “He was ripped when he came out of the womb.”

It runs in the family. Sandy Sr. is a solid 6-foot-1, 285 pounds. Sandy Jr., once a powerful high school running back nicknamed “Mack Truck,” is working toward his certification as a personal trainer. Yolanda says LeDarius, the youngest of the three at age 19, more than holds his own in the weight room.

At the same time, church and Bible study were a constant presence in their life.

“We were expected to help others,” Sandy Jr. said. “My parents were big on believing God would open doors for us, and Khalil never took that for granted.”

Sandy Sr. worked in corrections and later as a program specialist for at-risk youth, while Yolanda was a teacher.

Through childhood and adolescence, Khalil’s personality remained consistent. He was quiet, humble and respectful. Yolanda said there was never an issue with teachers at school and that one day in his freshman year at Westwood High, Khalil came home wearing a T-shirt that said “Citizen of the Month.”

As Christmas neared, the more loquacious Sandy Jr. would make sure his parents knew his gift preferences in order of importance, while Khalil seemed fine with anything that came his way.

The only way his parents could tell if Khalil didn’t like a gift is if he didn’t use it or wear it, because he never complained.

“He was always content with what he had,” Yolanda said. “He was always a peacemaker and his own leader. He never followed the crowd. I didn’t have to worry with Khalil about peer pressure.”

Yet when it came to sports, the otherwise laid-back Khalil transformed into a fierce competitor. Dad made sure of that.

Whether it was push-ups, basketball or brain teasers, Yolanda said her husband wanted the boys competing and striving to be the best, never doing anything halfway.

“He told us all the time, ‘If you’re going to do something, be the best,’ ” Khalil said.

Sandy Mack grew up competing against his twin brother Sammie and wanted the same for his sons, even if Khalil at times would be a little overexuberant.

“When we played basketball when he was young, I had to remind him, ‘You can’t be jumping on top of my head. I have to go to work tomorrow,’ ” Sandy said. “He really wants to be very good at what he does, and he’s been like that since he was a little kid. Real quiet, but when we played basketball or football, he was like a Tasmanian devil. He has a focus that is out of this world when it comes to sports.”

While the Mack boys played youth football, Sandy was reticent for Khalil to play for fear he might hurt someone. He’d been toughened up in backyard sessions with Sandy Jr., who said he went “beast mode” on his younger sibling.

When Khalil did play youth football, he ended up breaking the collarbone of a 12-year-old opponent on a tackle.

Sandy Jr. recalled the time he and his brother promised their late grandfather they would play in the NFL. Yet as Khalil got into high school, basketball was his first love, and he didn’t play football until his senior year.

With his son recovering from a torn patellar tendon, Sandy wanted Khalil to concentrate on graduating rather than playing football.

“I was thinking maybe the military for Khalil,” Sandy Sr. said. “All I knew was I wanted him out of Fort Pierce.”

That changed when first-year Westwood coach Waides Ashmon got a look at Mack and inquired why an athlete with the most impressive physique in school was not playing football.

Khalil told Ashmon to call his father, and the coach instantly whipped out a cellphone and promised Sandy Sr. his son would go to college for free if he played football his senior year.

The late start hurt recruiting, but Ashmon’s promise was kept when Buffalo came through with a football scholarship.

So Mack went from Florida to freezing winters in Buffalo, as usual, without a whisper of complaint.

“He was 1,300 miles away from us, and he never once called to ask for anything. Not a dime,” Sandy Sr. said. “He’d always say, ‘No, I’m good, pop.’ “

Mack impressed his coaches by working diligently, arriving early for meetings and breaking out a highlighter to go over practice plans and defensive assignments.

On the field, Mack began to realize his football career wouldn’t necessarily end at Buffalo.

During one practice, Mack ran around the blocking attempt of James Starks, a running back who went on to play for the Green Bay Packers.

“He told me, ‘Man, you’re strong. You’re going to the league,’ ” Khalil said. “That started to get me thinking.”

Mack began comparing himself with other players from the Mid-America Conference and watching players such as Von Miller, the No. 2 pick in 2011, and Dion Jordan, taken No. 3 overall in 2013.

“I knew they were probably playing against better people, but the NFL looked like something I thought I could do,” Khalil said.

A big game in a nonconference loss to Ohio State removed any doubt, and when Mack was available when the Raiders picked at No. 5 in the first round in 2014, McKenzie didn’t hesitate.

Khalil impressed veteran teammates as much with his attitude as his work ethic, even as a rookie.

“Khalil came in, picking my brain as soon as he got in, wanted to be great, and wanted to put in the extra work,” left tackle Donald Penn said. “He’s not a ‘me’ guy. He’s a team guy.”

Said veteran Marcel Reece: “I’ve seen first-round picks come in here and think the world should be handed to them. They’re prima donnas. They don’t think they have to work. They don’t think they have to practice. Khalil does what everyone else does — and then some.”

As a rookie, Mack stood out as a run defender, and while he pressured the quarterback consistently, he had just four sacks.

The only glitch came when the Raiders finally won their first game of the season against Kansas City after starting the season 0-10. After Sio Moore sacked Alex Smith with 28 seconds to play, the linebacker and Mack were busy performing a dance while the Chiefs quarterback rushed to the line of scrimmage to run a play.

Justin Tuck called timeout to prevent the Raiders from receiving a potentially crippling penalty.

It was a scene entirely in character for Moore, who offered regret with one-liners following the game. Mack, on the other hand, was mortified and embarrassed.

“Now,” Sandy Jr. said, “you’ve got to beg him to celebrate.”

Khalil instantly made an impression on Jack Del Rio, who took over for Dennis Allen and interim coach Tony Sparano in 2015. Del Rio knows a self-starter when he sees one, having been the position coach for Ray Lewis with the Baltimore Ravens from 1999-2001.

“With Khalil, the beautiful thing is that he’s got natural humility,” Del Rio said. “He loves this game, and he’s driven to play great. He wants to develop the skill level. He’s working tirelessly to do that.”

If there were any doubts that Mack was making a bull rush to stardom, they were erased in 2015, when he consistently stuffed the run and finished second to Watt in sacks with 15.

As he enters this season, Mack is trying to be more vocal, but his voice still occasionally trails off to a whisper and his general demeanor has not changed.

Teammates are occasionally awe-struck.

“It’s funny: Khalil doesn’t trash talk, he’s a very humble person, and he’s a really good guy,” tackle Menelik Watson said. “But once he gets into football mode, he’s going to rip your head off. It’s just that he’ll rip it off in a polite way.”

During training camp, Penn had been working on a pass blocking maneuver he was convinced gives him leverage, a quick jab he was sure would put Mack on his heels. Instead, Mack simply went lower than seemed humanly possible and blew past Penn.

“This dude, he somehow kept his balance,” Penn said. “He was two inches off the ground and kept rushing. I was all set to fall on top of him, and he just kept going. I asked (line coach) Mike Tice what I should do. He said, ‘I don’t have anything … good luck.’ “

Former Raiders linebacker Bill Romanowski said Mack’s ability to play both the run and the pass sets him apart from other edge players.

“If I had to compare Mack to anyone, it would be Von Miller,” Romanowski said. “Von may have a tiny edge in the pass rush because he’s a little smaller and a little quicker, but he can’t play the run like Mack. I think Mack is the more complete player all-around.”

Miller, last year’s Super Bowl MVP, signed a six-year, $114.5 million contract with a reported $70 million guaranteed.

The Raiders have Mack under contract through the 2017 season, and it’s conceivable the four-year, $18.6 million deal he signed as a rookie will be extended as an annual salary at some point in the near future.

It’s a huge commitment, but unlike a risky free-agent signing, the Raiders know exactly what they’re getting in terms of character and commitment.

“You’ve got to keep your stars. You pay it, and then you adjust the salary structure from there,” NFL Network analyst and former general manager Charley Casserly said. “Sometimes you try and beat the market and sign a guy early, but I don’t think they’ll worry about that with Mack. You don’t worry about it when a guy’s worth it.”

Herm Edwards, a former NFL head coach and ESPN analyst, compares Mack’s skill on the edge with Hall of Fame outside linebacker Derrick Thomas, whom he coached in Kansas City.

“When you pay that kind of money, it’s great for the locker room if it’s a guy you drafted,” Edwards said. “The Raiders know what they have. They know what his DNA is about.”

Included in Khalil’s DNA, according to his mother, is a penchant for coming home to Fort Pierce, visiting with neighbors and the same tight circle of friends he’s always had.

“I know that what he does has a lot of pressure that comes with it,” Yolanda said. “He’s worked hard for his accomplishments and knows that what he has can be here today and gone tomorrow. Our wish for him has always been to be balanced — live a balanced life.”

Watson thinks the $20 million a year threshold may be a bargain when it comes to Mack.

“Shoot, with the effort, intensity and attention to detail he puts in, he might be a $30 million a year a guy,” Watson said. “I really don’t think there’s enough money (under the salary cap) to give him what he’s worth.”

McKenzie understands that his boss would not look kindly at the sight of Mack in another uniform.

“Mark (Davis) would come beat me across the head if I let some Hall of Fame-type player leave the building,” McKenzie said.

Mack doesn’t plan on changing any time soon, regardless of fame and fortune. Anyone who saw him doing push-ups at a gas station years ago wouldn’t be surprised.

“It’s how I was raised. My parents put me in a nice position, but that’s all it is — a nice position,” Mack said. “You’ve got to put in the work. You’ve got to humble yourself.”