Ten-year-old Justin Reid didn’t stand a chance. His brothers, 13-year-old Ryan and 15-year-old Eric, were bigger, stronger and merciless.

"He was the baby, so my parents always treated him like a baby. Me and Ryan hated that, so we would always go that much harder on him,” the now 25-year-old Eric told NBC Sports Bay Area from the 49ers locker room after a recent practice. “Whether it was video games, sports or whatever. We just always made sure we beat him into the ground.”

Justin may have been smaller than his older siblings, but he was every bit as competitive. And he had a plan for payback.

“Whenever we weren’t around, he would just practice, practice, practice until he got better than us,” Eric said.

At age 12, Justin landed his first knockout in "Dragon Ball Z," one of the brothers' favorite video games.

“One day, I could never beat him any more at video games,” Eric said through a smile. “I was like, ‘OK. I guess I’m not playing that any more.’”

Beating his older brothers in something as frivolous as a cartoon video game was just a sign of bigger things to come. Justin is currently a safety on the Stanford football team. His drive to conquer the near impossible arrived with him on The Farm.

“I think we could ask him to do anything defensively, and he’ll find a way to get it done,” said coordinator Lance Anderson following a day of preparation for the Cardinal’s Pac-12 opener against No. 6-ranked USC. “He’s so driven to be good. All I have to say is, 'This is so hard. I don’t know if we can get this done.' He takes it personal. 'Yes, I can get that done. I can do that.'”

 

Justin plays special teams and seven different positions on defense – strong safety, free safety, boundary corner, field corner, the nickel, the dime and the X.

“His job will change from play to play depending on what position he’s playing,” said head coach David Shaw. “But Justin’s a playmaker: Make plays on the ball. Make plays on the runner. Make plays on routes.”

In Saturday's opener, coaches plan to put Justin mainly in position to disrupt the passing connection between quarterback and Heisman favorite Sam Darnold and his talented receivers.

“We’re going to try to get him matched up against their best guy as much as we can,” Anderson said. “There will be some opportunities where they play Deontay Burnett in the slot that will allow Justin to continue to play nickel and get matched up there a lot.”

Justin’s speed, athleticism, length and solid tackling ability make him just as important stopping the run, but his most important asset is his football IQ.

“He has really become a student of the game,” Anderson said. “He has such a great understanding of not only his position, but the whole defense now and how everything fits. I think that’s what’s helped him be able to move around to different positions. It’s just been seamless.”

“I feel like everything is moving in slow motion,” Justin said. “I can read keys so much quicker. I can go through a million checks in my head before the play even starts, and I can anticipate -- not guess -- what the play is before it even starts. It allows me to play faster than I’ve ever played before.”

And consider, Justin’s play his sophomore season was fast enough to land him on the watch list for the Jim Thorpe Award, which recognizes the nation’s top collegiate defensive back.

Justin's biggest mentor, helping him take his football skill to new levels, is the same agitator who was once determined to pummel him into non-existence. The sibling rivalry between Eric and Justin evolved into a brotherly bond over football once Justin started playing in high school.

“And I was out of the house, too,” Eric added, laughing.

Eric grew up to become an All-American at LSU and a Pro Bowl safety in his rookie year with San Francisco. Their dad, mom and older sister, Christina, also went to LSU, but Eric pushed Justin to attend Stanford. He saw the football program and the academic opportunities as a perfect fit for a brother he calls an "extremely bright kid."

“It’s the best choice of my life,” Justin said.

The brothers get together in Eric’s South Bay home whenever their schedules allow (and whenever Justin is hungry for a home cooked meal by Eric’s wife, Jaid) so that Eric can break down Justin’s Stanford games as well as his own from the NFL.

 

“He’ll give me tips on what things worked for him in college and also what things will work for me in college now,” Justin said. “He teaches me things from an offensive perspective about what [opponents] are trying to do. Then, when you can see that as a defensive player, you better know how to counter it. You can almost start baiting it so you can steal plays away from them.”

“I always tell him the difference between good and great players is the mental aspect, especially when you get to the League. Everybody’s big. Everybody’s fast. Everybody’s strong,” Eric said. “I tell him not to try to make big plays, let them come to him based off what he knows is happening.”

Justin has to know what is happening with Stanford’s entire defensive secondary, considered one of the best in the Pac-12 this season. But his knowledge goes beyond the in-game responsibilities of a safety or even a team captain.

“I’m so intrigued by football and the playbook. It’s stimulating to me,” Justin explained. “I always like to keep venturing out and learn more positions and learn what each player on the field is thinking. Because knowing what they’re thinking allows me to see, allows me to anticipate what they’re going to do on the field so I better know how to protect them, and I better know how to do my responsibility, because I know what the strengths of the coverage are and I know the weaknesses of each coverage are.”

“He’s a great communicator,” Shaw said. “Part of his job is to make sure everybody else knows what they’re doing, and then everybody’s got to play fast.”

It can be a lot to take in, and there is no easing into it as the Cardinal will face many of the nation’s top quarterbacks and offenses in the Pac-12 this year, starting in Los Angeles this weekend.

“We live for games like this,” Justin said. “It’s a great challenge for us to show the conference and show the whole world what type of defense we really are.”

Eric will be watching, even as he prepares to stuff Cam Newton and Justin’s former Stanford teammate, running back Christian McCaffrey, in the 49ers' season opener against the Carolina Panthers on Sunday.

The NFL chatter that comes with the start of each collegiate season already includes Justin’s name. Eric has been there. He entered the draft after his junior year at LSU and became a first round draft pick of San Francisco. He's advised his younger brother to stay focused on school and football and let their dad handle any off-the-field NFL business, just as he did for Eric. They’ll decide what’s best for Justin after the season.

 

“The more he plays, the stronger he gets,” Eric said. “I’m excited to watch him play this year.”

Eric and Justin are now the same height, 6-foot-1, though Eric has a nine-pound advantage. Where he once saw a childhood adversary, he now sees potential that may surpass his own. Eric can now admit that Justin just might be the fastest of the three Reid brothers.

“But never let him know I said that,” he added quickly.

Some sibling rivalries are never outgrown.