One of the most impactful scenes in “Concussion” is a brief and wordless one — just a few seconds, really, of a high school football team going through its drills.

We don’t know who these young, determined, helmeted kids are, but the message is sobering, especially if you’re a parent: Concussion-related brain damage from football is not merely a threat to the professionals featured in the film. It’s a threat to our football-playing kids, too.

And that’s a strong argument for any football lover (or parent of one) to see this film, which is anchored by a sensitive, understated performance by Will Smith as the real-life forensic pathologist who earned the NFL’s animosity for shining a torch on the problem in Pittsburgh, home of the revered Steelers.

The film, directed and written by Peter Landesman, may suffer from an overly simplistic, sometimes sermonizing script that could have used some sharp editing. But it’s to be admired for bringing a truly important issue to the big screen.

We first get to know Dr. Bennet Omalu, a Nigerian immigrant, in the autopsy room, where he has the strange habit of speaking to the corpses he’s cutting into, asking them questions. He wants their help, in deducing how they died.

One day, a beloved former Steeler ends up on Omalu’s table: Mike Webster — “Iron Mike” — who died at only 50 after his last years were plagued by dementia. Omalu wonders why a high-level athlete would experience such a rapid deterioration. Ignoring colleagues’ pleas to leave the case alone, Omalu orders testing of Webster’s brain, at his own expense. “I don’t know what I’m looking for,” he tells his skeptical but supportive boss, Cyril Wecht (a wisecracking Albert Brooks.)

What he discovers is shocking: Webster’s brain has been ravaged, a result of repeated blows over his long career — some 70,000 hits, Omalu estimates. He co-authors an article in a medical journal outlining his findings that Webster and others like him suffer from CTE (chronic traumatic encephalopathy). He thinks the NFL will be glad to know, so it can better help its athletes.

Well, he’s wrong. There’s been some controversy over whether the “Concussion” filmmakers may have deleted scenes to mollify the NFL, but the NFL certainly does not look good here. Rather than welcome Omalu’s findings, the league and its representatives seek to discredit him. Wecht tries to explain this to an oblivious Omalu, who doesn’t watch football (or even turn on the TV).

Or, as former Steeler doctor Julian Bailes (Alec Baldwin) tells him: “You gave their biggest boogeyman a name.” Bailes has watched a string of players die under tragic circumstances, including the suicides of Junior Seau in 2012 and Dave Duerson a year earlier. (Duerson’s family, incidentally, has publicly disputed how Duerson is portrayed in the film.) He turns into a crucial ally of Omalu’s.

Much of the credit here goes to Smith: He masters Omalu’s Nigerian accent in a convincing, unshowy manner, and remains hugely watchable throughout. Baldwin is effective, too, though his own accent is uneven. As Omalu’s future wife, the gorgeous Gugu Mbatha-Raw is touching but seriously underused — and saddled with more heavy-handed lines than she deserves.

It is she, though, who points out a deep truth to Omalu: Football, she tells him, is a beautiful game. But it also has a dark, troubling side that many have been loath to acknowledge, and that’s a simple reason that “Concussion” is a worthy enterprise indeed.