Sebastian Castro was afraid to take hits from the older kids as a child in the neighborhood backyard football games. Now the Iowa defensive back is one of the hardest hitters in college football.

Castro, a fifth-year senior, is by no means the biggest player when he steps on the field. But at 5-foot-11 and 205 pounds, he uses his size to his advantage, running hard downhill toward the ball and throwing his body at its carrier.

And he remains a leading defender not just at Iowa and in the Big Ten conference — but in the nation. And he has been off to a hot start this year.

Castro, who was named a midseason second-team All-American by the Associated Press in October, leads a stout Hawkeye defense in pass deflections with four and interceptions with three — the latter good for third in the Big Ten and 25th in the country. 

“Coming to Iowa and having to wait to play and just learning the whole time [was] a humbling experience,” Castro said. “I’m glad it happened.” 

Iowa third-year defensive lineman Yahya Black said the Hawkeye defense can always depend on Castro being in the right position to make a play. 

“He’s a pretty soft-spoken guy, but he’s all business,” Black said. “When it comes time to play, he doesn’t miss.”

Castro’s “all business” mindset developed early in his youth in a family that emphasized work, culture, and one another over anything else.

Castro grew up in the Chicago southwest suburb of Oak Lawn alongside his mother and older brother, Roque. 

Castro was only one month old when his father was sent to prison, so the Castros lived with his grandparents, Jose and Teresa Gonzalez — leaving both him and his brother to admire their grandfather as a positive role model.

“He’s the provider and protector of his family,” Castro said of his grandfather. “I always looked up to him.”

And Jose’s household would often fill up to nearly 10 people as Castro’s much older and much bigger cousins frequently joined them in living in the home.

“It was definitely a family that pushed hard work and that nothing was given to you,” Roque said. “Just because you have a big household with many people, that doesn’t mean that you can just slack off. Everyone had a job, and everyone had to do their part.”

So with kids of all ages running around the Gonzalez home, Castro grew up filling his free time recreating — or rather serving as the victim of — professional wrestling moves in the backyard with his older cousins and brother.

“We would actually be afraid of our cousins because they were so big,” Roque said. “They were just using WWE moves every time they came over … because we were the smallest kids.”

But the cousins often opted for brutal and violent tackle football games — games Castro believes developed his hard-hitting mentality as a player today. 

“We didn’t play with pads,” Castro said in an interview with Our Esquina. “I got used to the physicality. We played tackle. We didn’t care.”

Roque would often use competitive games of one-on-one driveway basketball against Castro to exert his own force upon his little brother.

But after one game when Castro was in eighth grade, in which he had enough of his older brother pushing him around and finally fought him back, Roque realized the strength, physicality, and pain tolerance his younger brother truly possessed.

“Playing with older kids growing up, I was scared to go against them because I didn’t know what it felt like to get hit like that,” Castro said. “Once I realized it wasn’t that bad, I just embraced it.”

Castro learned the game of football from Roque, who is four years his senior and played defensive back for St. Xavier University, an NAIA school located in Chicago.

But Castro always preferred video games, climbing, and keeping to himself as a child. Rarely was football on his mind.

Roque would often need one more player for his seven-on-seven football games with friends, forcing Castro to come despite his reluctance.

And as Roque practiced footwork and tackling drills, Castro slowly picked them up, finally joining Roque in the drills when he reached eighth grade and allowing his older brother to coach him through what angles to take and how to read the opponent’s hips.

One year later, Roque found his brother’s footwork had already surpassed his.

“He’s always been very talented,” Roque said. “He just combined talent with hard work, and then that’s just when his football career blew up.”

Castro’s love for the game only grew as the games in the backyard with his family quickly evolved into suiting up for Richards High School, his fear of taking a hit developing into a talent of hitting others. 

Castro excelled for the Bulldogs, propelling the team to the state playoffs in three consecutive seasons and earning him first-team All-State honors as both a junior and senior.  

He finished his last season of high school with 95 total tackles, 6.5 tackles for loss, and six interceptions. 

Castro’s high school success earned him a three-star recruit status as well as offers from Power Five schools such as Iowa State, Minnesota, and Syracuse. But he was surprised at what Iowa could offer him following a visit in his junior year.

“When I first came here, I really knew nothing about Iowa,” Castro said. “But when I just saw how everyone operated and the production and consistency they had, [committing] was almost like an easy decision.”

Castro became a Hawkeye in June of 2019.

The 23-year-old admits he was humbled his first few years at Iowa, struggling to see any meaningful playing time early on in his tenure in a Hawkeye defensive back room that consisted of a group including future NFL players Geno Stone and Michael Ojemudia.

Castro redshirted in 2019 and appeared briefly in just one game during the COVID-19-shortened 2020 season. He saw action in all 14 games in 2021, racking up six tackles but playing mostly on special teams.

Despite the playing time, Castro was disappointed. He wanted more.

“I was a star player in high school, and I think I’m going to walk into Iowa and just start,” Castro said of his first year. “I had the talent, but I wasn’t a good player. That was hard for me to accept as an 18-19-year-old.”

In a landscape marked by college athletes who can transfer schools and see game action without sitting out a year, most players in Castro’s position would choose to take their talents elsewhere instead of losing playing time as the years went by.

But he remained patient with his role in the program and took the time in the early stages of his college career to master defensive coordinator Phil Parker’s defensive scheme.

And as he absorbed the Hawkeye defensive way, he caught the eye of coaches on the scout team as he competed both with and against defensive backs and future NFLers Riley Moss and Dane Belton. 

“I heard rumors of what he was doing on the scout team his freshman year and how [coaches] would get mad at him for tackling guys,” Iowa linebacker Jay Higgins said of Castro. “But he’s one of those dudes who just sits in Coach Parker’s room and listens to everything he says.”

It wasn’t until last season that Castro’s role on the defense increased; he started eight games at the Cash position — a hybrid position of a defensive back and linebacker only Iowa employs — and finished the season with 33 tackles, two forced fumbles, and one sack. 

That season included a career-high five tackles in Iowa’s 21-0 Music City Bowl win over Kentucky on Dec. 31, 2022, propelling him into his fourth year this season.

In Iowa’s Sept. 9 matchup with rival Iowa State, Castro snagged his first career interception for a touchdown. 

On a clever read of the Cyclone receiver’s curl route, Castro sprinted ahead and caught the ball before anyone could do anything about it, waltzing to the end zone untouched and propelling the Hawkeyes to the 20-13 win.

And Iowa head coach Kirk Ferentz took note.

“He’s an aggressive, tough guy who is totally committed and 100 percent onboard,” Ferentz said after that game. 

Castro then had his best game of his college career a month later in Iowa’s 15-6 win over Wisconsin on Oct. 14 — making a career-high seven tackles, two tackles for loss, one pass break-up, a blitz for a safety, and the game-winning interception.

But he’s been making an even greater impact on opponents, literally, as he lays the bone-rattling hit stick on anyone running his way.

That’s a feeling Wisconsin running back Braelon Allen learned all too well when the 5-foot-11, 205-pound defensive back pounded the 6-foot-2, 245-pound running back on a fourth-and-one play late in the game. Allen even briefly lost the ball upon the hit.

This play by Sebastian Castro is ridiculous. Castro, listed at 5-11 205, stops Braelon Allen, listed at 6-2 245, dead in his tracks. Honda Civic meets Ford F-150 and Honda wins. Wisconsin retained possession but Aaron Graves cleaned it up shortly thereafter. pic.twitter.com/31Hw0wPR99

— Tyler Tachman (@Tyler_T15) October 15, 2023

“[Castro] hits hard; everybody sees it,” said Iowa running back Leshon Williams, who has had his fair share of Castro hits as the two went head-to-head in practices as high school teammates. “When he hits people, they go down.”

Castro approaches his hard-hitting tackles in a methodic, even psychological way; the fear of a crushing Castro hit looms in opposing running backs’ and receivers’ minds.

“I feel like it’s affecting [the opponent’s] game because in the back of their mind, they know that I can just come out of nowhere and hit them,” Castro said. “That’s the mental part of the game I try to enforce because, whether or not they know [where I am], that’s breaking them down slowly and slowly.” 

Castro’s performances so far this season have been a bright spot on a 6-2 Iowa team still in the running to compete for a Big Ten Championship despite offensive injuries and struggles — and have served as a testament to his commitment to developing as a player.

“I made a deal with myself that until you start playing at a high level consistently all the time, you don’t have the right to transfer,” Castro said. “I felt if I did [transfer], I would regret it.”

And it’s safe to say he would have missed out had he given up on the Hawkeyes, his NFL Draft stock now slowly rising with each game this season.

Castro didn’t think his football career would change so fast, from a to-be senior hoping for significant snaps this year to a midseason All-American with options to play professional football or come back to Iowa for one last ride.

“It’s been crazy how fast it’s changed up on him, and he’s still trying to understand [it],” Roque said. “I don’t think it’s really settled in yet.”

But his success today all dates back to the scrappy backyard football games with his cousins, to taking painful hits that he once feared but now imposes upon his opponents two decades later.

“I feel like a lot of family or friends think it’s just like, ‘Oh, wow, it just came out of nowhere. He’s always had this,’” Roque said, noting how proud he is of his brother’s process. “No. It wasn’t just something that he woke up one day and started doing … He obsessively worked at it.”