CHICAGO — Alfonzo McKinnie was in a film class his junior year of high school when he first watched “Hoop Dreams,” the 1994 documentary about two African American teenagers from inner-city Chicago who eyed professional basketball careers.

As he sat in that classroom at Chicago’s Marshall High, McKinnie felt a kinship with one of the film’s protagonists, Arthur Agee, who grew up in the same rough neighborhood on the city’s west side and also attended Marshall. These days, McKinnie sometimes rewatches “Hoop Dreams” to remind himself that he is not so different from Agee, one of thousands of young men in Chicago hoping that basketball can be their ticket out.

The biggest difference between Agee and McKinnie is that, though Agee’s basketball career ended with a two-year stint at Arkansas State, McKinnie’s is just beginning to flourish. A 26-year-old small forward, he has found his NBA footing as a rotation player for the Warriors.

Playing in front of more than a dozen family and friends Monday night at Chicago’s United Center, just a 12-minute drive from his childhood home, McKinnie recorded his first career double-double with career highs in points (19) and rebounds (10). His four three-pointers in that rout of the Bulls matched his total through Golden State’s first seven games of the season.

“If it wasn’t for Klay, we’d be talking about ’Zo tonight,” Kevin Durant said, referencing Klay Thompson’s NBA-record 14 three-pointers.

But the highlight of McKinnie’s day came hours earlier, when he signed the final papers to purchase a house in Chicago’s suburbs for his mother, Elisa Bryant.

It was Bryant who awoke at 5 a.m. each weekday to work at a post office so she could provide for McKinnie and his younger brothers. It was Bryant who signed up McKinnie for youth basketball leagues to keep him away from neighborhood gangs, with their street corners promising casual violence. It was Bryant who, when McKinnie was playing in the rec-league-size gyms of Luxembourg, told him not to give up.

“She’s been there from Day 1,” said McKinnie, who will make more than $1.3 million this season. “Anything I can do for her, I’d break my back to do.”

McKinnie wasn’t supposed to be one of the lucky few from Chicago’s West Side to reach the NBA.

As a rail-thin senior at Marshall High, he was the Commandos’ third-leading scorer and second-leading rebounder. It wasn’t until after his final game with Marshall that McKinnie academically qualified to play at a Division I college. After two seasons at Eastern Illinois, he transferred to Wisconsin-Green Bay, where he twice tore the meniscus in his knee.

McKinnie’s senior stats with the Phoenix — 8.0 points and 5.3 rebounds per game — deflated any thoughts he had of getting drafted to the NBA. With no other pro offers, he signed with the East Side Pirates of Luxembourg’s second division, where his teammates held down 9-to-5 jobs to pay their rent.

After playing in Mexico and on a traveling 3-on-3 team, McKinnie paid $175 in September 2016 to try out for the Windy City Bulls, the new NBA Development League team in the Chicago suburb of Hoffman Estates, Ill. By the time he scored 16 points in the D-League All-Star Game five months later, McKinnie began to think the NBA was attainable.

He briefly made Chicago’s roster before last season, only to be one of the team’s final cuts in training camp and finally catch on with Toronto. After getting waived by the Raptors in July, McKinnie joined Golden State for training camp in hopes of securing its remaining two-way contract.

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Three weeks ago, while on a team charter from Las Vegas to San Jose for the Warriors’ preseason finale against the Lakers, head coach Steve Kerr informed McKinnie that Golden State was signing him to a two-year minimum contract. With restricted free agent Patrick McCaw yet to re-sign, the Warriors were giving their 14th roster slot to McKinnie.

“There was a point in time where I didn’t expect anything like this to happen,” said McKinnie, speaking to reporters Monday evening in the tunnels of the United Center. “I wanted it to happen, like crazy. But at the time, it wasn’t looking promising.”

McKinnie paused to glance up at Durant, who was walking past the media scrum with a team security guard. “Look at you, ’Zo!” Durant yelled with a smile. “I see you!”

Little more than an hour later, McKinnie entered the game against the Bulls midway through the first quarter to a loud cheer. Admittedly nervous, he missed a 9-foot jumper, grabbed the offensive rebound and clanged a layup attempt.

With Thompson commanding the defense’s attention, McKinnie hit a three-pointer late in the first quarter before drilling two more threes early in the second. Watching courtside was one of his childhood idols, Bulls great Scottie Pippen. After the final buzzer, McKinnie returned to the visitors’ locker room to find his iPhone flooded with congratulatory texts from childhood friends.

“Being able to do it here in Chicago, my home city, in front of all my family and friends, it was amazing,” McKinnie said. “I’m just hella excited.”

A versatile defender who can move off the ball and isn’t afraid to take the open jumper, McKinnie seems an ideal match for Kerr’s system. Stephen Curry recently proclaimed that McKinnie is “not even close to scratching the surface on what type of player he’s going to be,” going as far as saying that, “it would not surprise me if he’s a huge, huge catalyst for us — especially in those games that matter at the end of the year.”

It was high praise for a player who is well aware that, had he not seized a couple of opportunities, he easily could’ve been another athlete from Chicago’s West Side whose career topped out in college. That is why this past summer, at his basketball camp in his childhood neighborhood, McKinnie brought in Agee as a guest speaker.

“I’m kind of living the hoop dream, just being a kid from the West Side of Chicago like Agee was,” McKinnie said. “I was able to go further in my basketball career. But I looked up to guys like him, just seeing where he came from and how he was trying to overcome things. I just related to it.”

Connor Letourneau is a San Francisco Chronicle staff writer. Email: cletourneau@sfchronicle.com Twitter: @Con_Chron