Five years ago, Haggai Ndubuisi didn’t know what a first down was. And he certainly didn’t know what a blitz was.

Ndubuisi at the time was playing soccer and basketball in his native Nigeria. He had heard about football but knew next to nothing about it.

“American football was foreign to me,’’ he said. “I thought football was just maybe people running into people.”

Well, much of it actually is. And if Ndubuisi, 22, can progress well enough to run into the right people, the Broncos just might have something on their hands.

The defensive lineman joined the Broncos last month as part of the NFL’s International Player Pathway Program, which provides international players an opportunity to earn a spot on a roster. He has gone through 10 organized team activity practices with Denver and will take part in a mandatory minicamp Tuesday through Thursday at Centura Health Training Center.

Ndubuisi then will be back for training camp in late July. Until the final roster cutdown to 53 before the start of the regular season, he doesn’t count against the Broncos’ 90-man offseason NFL roster limit.

“OTAs went great,’’ Ndubuisi said. “It gave me multiple opportunities to learn and try to get better at what I do because this is our job.”

The 6-foot-7, 323-pound Ndubuisi is Denver’s tallest and second-heaviest player on defense. He grew up in Enugu, Nigeria, first being a forward in soccer and later a center in basketball after he had a growth spurt.

Then in 2018, when Ndubuisi was 17, Ejike Eugoaboa, a former basketball player in Nigeria, suggested he give football a try.

“So I started watching football on YouTube and practicing,’’ he said.

Ndubuisi found himself sometimes practicing alone since football hardly is popular in Nigeria. But Eugoaboa by 2021 hooked him up with Osi Umenyiora, a former New York Giants and Atlanta Falcons defensive end who was born in London to Nigerian parents and runs the UpRise Academy in Ghana, which works with the NFL to find talent in Africa.

Ndubuisi eventually was selected to attend a one-week camp in London and then a 10-week International Pathway Program camp in Arizona. He was allocated to the Arizona Cardinals and went to training camp with them in 2022.

Ndubuisi was then an offensive lineman and he didn’t make the Cardinals’ roster. But Ndubuisi this year was moved to defense and he took part in a 10-week International Pathway Program camp in Bradenton, Fla., before being allocated to the Broncos.

“I love defense,’’ he said. “I just love to run into people. It makes me happy. I don’t care what’s in front of me. I just go through whatever it is I have to go through.”

Of course, it’s not that easy. Broncos coach Sean Payton said he must see more from Ndubuisi before making a full evaluation.

“He’s doing well,’’ Payton said after OTAs. “The biggest challenge (is) no one’s got shoulder pads on or anything yet. He looks good. He’s smart and I like him. I think it’ll be easier for me to (evaluate him) seven days into training camp.”

Linebacker Josey Jewell said Ndubuisi has “got some length” and is “very strong.”

Ndubuisi is the only player on the Broncos’ roster who didn’t attend college. However, tight end Chris Manhertz also didn’t play college football, having been a basketball player at Canisius.

“I wish I had the opportunity to play in college, and I would have been way better than I used to be,’’ Ndubuisi said. “But it’s a process and I have to believe in the process and just get better. It’s a difficult transition. But I feel like I’m getting better. I feel like the coaches are really doing a great job and I feel I’m blessed.’’

The odds are against Ndubuisi, but he is determined to make the NFL and wants it to be a family affair in America when it comes to pro sports. His younger brother, Timothy Chiki Ndubuisi, is a 7-2 center playing basketball in Italy, and Ndubuisi believes his brother could make the NBA.

If Ndubuisi were to earn a roster spot, he would become the fourth Broncos player to have been born in Nigeria. The list includes linebackers Jeremiah Attaochu and Patrick Chukwurah and defensive end Willie Oshodin, but all played college football in the United States.

Oshodin, who came to America when he was 12 and played for Denver from 1993-95, was intrigued to hear about Ndubuisi’s signing and plans to follow his progress.

“He must be an athlete,’’ Oshodin said.

Indeed Ndubuisi is. He said he held his own in soccer and basketball but has left those sports behind for good.

“Football is now my life,’’ he said.