There's a relentlessness to "Unguarded" — the latest documentary from ESPN Films, which premieres Tuesday night at 8 p.m. ET — that makes it both difficult to watch and impossible to turn off. Over and over, viewers are confronted by unsettling mental images, uncomfortable silences and the steady, unavoidable story of a stomach-turning descent.

It's a film born of pressure: the pressure of carrying a city on your back and hiding your darkest secrets from the people you love; of desperately searching for escape and finding every exit barred, of omnipresent addiction digging ditches in your stomach and screaming bloody murder in the back of your head. But despite its weight, "Unguarded" isn't chaotic; it's got the practiced pace of a story told countless times in countless rooms for countless people.

It should. Because this is the story of Chris Herren, a New England basketball legend turned addict in recovery. It's a story he tells again and again, wherever he can, in the hope that he can help people avoid the mistakes that nearly killed him. And, at the risk of sounding crass, it's a story that makes for a hell of a movie.

Much of the credit for that goes to Jonathan Hock, the award-winning filmmaker behind acclaimed sports documentaries like "Through the Fire," which traced highly touted high school point guard Sebastian Telfair's path from Brooklyn's Surfside Gardens projects to the bright lights of the NBA, and "The Best That Never Was," the story of how shooting star running back Marcus Dupree shined for the University of Oklahoma before burning out and fading away. As Patrick Goldstein of the Los Angeles Times wrote in a recent piece on "Unguarded," Hock's films tend to center on "lost souls."

Chris Herren certainly qualifies.

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In 1994, Herren was golden. He was the fighting pride of Fall River, Mass., a third-generation star athlete named to the McDonald's All-American Team, a tough-as-nails point guard who eschewed recruitment by national hoops powerhouses to stay home and play at Boston College.

Over the next 15 years, he squandered his talents and numerous chances by abusing a litany of drugs, including cocaine, heroin, OxyContin and crystal meth. That he's not dead is something of a miracle.

Game footage of Herren showcasing his talents, both at Durfee High School and, later, at Fresno State University, show us why he mattered to the wide world of sports and why we should care that things fell apart. We see Herren penetrate with panache, exploiting openings to find teammates with dump passes or finish at the rim.

We see him drain jumper after jumper from all over the court and show pretty impressive springs for a 6-foot-2 lead guard; in fact, one shot of Herren elevating for a weakside alley-oop calls to mind a similar archival clip of Bethel (Va.) High School star Allen Iverson from Steve James' excellent film "No Crossover," part of ESPN's "30 for 30" series.

The two talents are linked again later in the film, when Herren references a November 1994 Sports Illustrated cover story on the resurgence of the Big East that focused on the highly anticipated arrival in the conference of three big-time guards: Iverson at Georgetown, Felipe Lopez at St. John's and Herren at Boston College.

Two weeks after that SI article came out, Herren says in the film, he entered his dorm room at Boston College to find his roommate and two girls chopping up lines of cocaine. He'd been a hard drinker and partier in high school, he says, but this was his first encounter with coke. He was 18 years old.

"That day ... opened doors for me that I was not able to close for the next 15 years," he says.

Iverson starred at Georgetown for two years before becoming the top selection in the 1996 NBA draft and embarking on a Hall of Fame career. Lopez never quite lived up to his recruiting hype, but he finished his college career as the third-leading scorer in St. John's history and was chosen in the first round of the 1998 NBA draft, spending four years in the league.

Herren, however, broke his wrist in his first game at Boston College and missed the rest of his freshman season. While on the shelf and away from supervision, he began using drugs regularly, failed multiple drug tests and found himself out of Chestnut Hill within a year.

Addiction and run-ins with the law marked the remainder of Herren's basketball career, which included three years running point for Jerry Tarkanian at Fresno State, 70 games in the NBA with the Denver Nuggets and Boston Celtics, and overseas stints with clubs in Italy, Turkey, China and Germany.

Tarkanian cuts an engaging, emotional figure during his scenes in "Unguarded," breaking down in tears multiple times as he discusses Herren, whom the former UNLV coach gave a second chance. During a talk in Fresno, Tarkanian raises the idea that Herren's biggest problem might have been that every time he did something well, a couple more people from Fall River came out to California to see him.

The coach isn't the only one to suggest that many of Herren's problems stemmed from the group of lifelong friends from the old neighborhood with which he surrounded himself; his brother Mike notes that those friends "who weren't caught up in the hype" were the only ones Chris truly trusted. That pressure — to succeed as the conquering hero and put your city on the map without forgetting where you came from and who helped you rise up — is a very common trope in the world of sports, and especially in basketball.

But it's much, much more frequently referenced in the backgrounds and creation myths of black athletes than white ones, which is why it's fascinating to see it portrayed so plainly in Herren's story ... and kind of disappointing that the racial element of it is left mostly unexplored in "Unguarded."

It would have been interesting to see at least a little consideration of Herren's role as the great white homegrown hope, especially at predominantly white and Irish Catholic Boston College, as well as the fact that Herren, for all athletic purposes, didn't wind up "escaping the streets." Failure of that sort is the type of thing that some sports fans like to use as a cudgel to bash athletes, especially black ones, who wash out rather than reach stardom. In the context of Chris Herren's story, I wonder if those folks will see things a little differently.

By 2008, Herren had spent every dime he'd made in his professional basketball career and overdosed four times. In "Unguarded," Herren tells a variety of audiences the stirring story of how he fell, repeatedly, and how he eventually found his footing. He is now 36 years old; as of filming, he had just reached three years of sobriety.

We see Herren talking to students, military personnel, prisoners and recovering addicts in myriad settings, with Hock splicing the disparate talks together into a linear narrative. That the story remains constant even as Herren's clothing and surroundings change evokes the feeling of a steady journey or pilgrimage — the idea that the mission he's out to accomplish doesn't change, even though the scenery and audience do.

We're made to feel that going from place to place to tell this tale is now Herren's purpose, and that perhaps having to repeatedly revisit his darkest times is his penance. Late in the film, Herren acknowledges having found his calling: "I find a certain peace with what I do today. I didn't find that peace in basketball. I never did."

Herren's delivery of his often-dismal story remains constant and unflinching, and so does Hock's portrayal of it. The dark places in Herren's past are very clearly illuminated; we travel with him to the Modesto, Calif., 7/11 where he slept on the street and considered abandoning his wife and children. Just after Herren relates the harrowing memory to an audience of shaken-up addicts, Hock has Herren stand on the actual spot and tell it to us one more time. These repetitions feel like steady, jarring jabs; over the course of "Unguarded," the effect adds up. By film's end, you may find yourself gasping for air.

"Unguarded" airs Tuesday, Nov. 1., at 8 p.m. ET on ESPN. An encore presentation is scheduled for 7 a.m. Saturday on ESPN 2.