It’s doubtful the filmmakers behind “Snitch” originally had Dwayne “the Rock” Johnson in mind.

They probably pictured casting an Oscar nominee like Edward Norton, Matt Damon or Jeremy Renner as a 40-ish suburban dad who gets deep into trouble when trying to save his incarcerated teenage son.

Instead they get the 6-foot-4 former World Wrestling Entertainment champ, who looks as if he could crush a villain’s head between his thighs.

And yet … Johnson delivers, for the most part, with his best performance and best film to date. An engrossing balance of drama and thriller, “Snitch” introduces a minefield of compromised morality, where every action taken or not taken could lead to a worse predicament for its hero.

Johnson plays John Matthews, a wealthy construction company owner who is remarried and living the good life in Jefferson City (but the film was shot in Louisiana) with a young wife (Nadine Velazquez) and daughter (Kyara Campos).

When son Jason (Rafi Gavron) from a previous marriage gets naively roped into an Ecstasy trafficking scheme, the youth faces a mandatory minimum prison sentence of 10 years.

With few options, John proposes a risky deal to the federal prosecutor (Susan Sarandon): He’ll work as an undercover informant, using his company’s trucks to run drugs in exchange for Jason’s reduced sentence. But things spin out of control as his desperate mission crosses paths with a Mexican drug cartel, jeopardizing the safety of both his families.

It’s a compelling scenario established by writer/director Ric Roman Waugh (“Felon”) and co-writer Justin Haythe (“Revolutionary Road”). Inspired by a PBS “Frontline” episode about how U.S. trafficking laws affected the family of James Settembrino, they ground the setup in reality rather than mold it into a mindless action vehicle a la “Taken 2.” What makes the picture consistently interesting is that the stakes aren’t just high for the hero but for everybody involved (and for quite different reasons).

Former stuntman Waugh surrounds his star with fine performers, including Barry Pepper as a jaded DEA agent sporting a nu metal goatee who heads the sting operation. He provides advice on how to act covert: “Just be yourself, John. Try and be something you’re not, they’re bloodhounds. They’ll smell it right away.”

Most impressive is Jon Bernthal as John’s ex-con employee, whom he bribes into helping arrange an introduction with a local drug kingpin (Michael Kenneth Williams of “The Wire”). Bernthal (so memorable as Shane on TV’s “The Walking Dead”) portrays a man also trying to do the right thing by his family, which means avoiding the criminal life — the opposite of what John needs him to do.

“Snitch” becomes a bit reliant on the “shaky cam” style of filmmaking. Is it really necessary to shoot a scene with two people talking in a room as if the cameraman were jogging on a treadmill? The movie also unleashes two huge action sequences that, while impeccably staged, are almost too Hollywood for this character piece. It’s debatable whether they bolster or detract from the storytelling as a whole.

But the nagging question remains whether “Snitch” could have benefited with a more “serious actor” as its lead. The Rock remains a charismatic star with a sharp sense of humor, and he’s admirably attempting to transition into substantive adult roles. Yet he’s sometimes overmatched by the introspective aspects of the script and by his fellow actors.

Fortunately, he’s playing a character who is also in way over his head. Perhaps his palpable discomfort over a new challenge ultimately bolsters this formidable drama.