Brad Pitt in “Killing Them Softly.” (Melinda Sue Gordon/Cogan’s Productions)

As noted in today’s morning mix, “Killing Them Softly” — a gangster picture that re-teamed Pitt with his “Assassination of Jesse James” director Andrew Dominik — opened in seventh place with $7 million. That’s less money than the debuts of “Seven Years in Tibet,” “Meet Joe Black” and “The Mexican” generated, without even adjusting for inflation.

It’s a somewhat surprisingly dismal performance for a film starring an actor who, at this time last year, was riding a wave of best picture buzz in two films, “The Tree of Life” and “Moneyball.” It’s also notable that ”Killing” didn’t, well, die because of bad reviews. It was well received by some critics, earning a 78 percent positive rating on Rotten Tomatoes. That’s a stronger skew than past award-worthy Pitt projects such as “The Curious Case of Benjamin Button” and “Babel.” So, what happened here?

Most likely, a combination of factors prevented “Killing Them Softly” from popping at the multiplex. But these two seem like the most potentially significant.

1. Lack of marketing.

Most of the hype about “Killing Them Softly” was built in the 11th hour, with a few Pitt interviews that circulated in the days just before the movie’s release. Commercials for it aired, sure, but not many, or at least not many that stuck in the memory. If I were to walk outside The Post newsroom right now and do a man-on-the-street survey asking people why they did not see “Killing Them Softly” this weekend, I suspect 80 percent of them would not know what I was talking about, 15 percent would think I was referring to either a Roberta Flack or Fugees song and 5 percent would mistakenly believe I was quietly threatening to commit murder.

My sense is that the public was largely unaware this movie existed, and that those who knew its title were still fuzzy on its premise. Therefore, it was overshadowed by things people do have some basic grasp on: Bella Swan, James Bond and Abraham Lincoln.

2. The irrelevance of star power

The lack of excitement about “Killing Them Softly” doesn’t mean moviegoers no longer care for Pitt. But it does remind us once again that star power — particularly of the Pitt or Tom Cruise variety — does not carry nearly the kind of weight with moviegoers that it once did.

Ticket buyers are far more influenced by a plot concept, familiarity with a franchise, overall buzz or what their friends are saying on Twitter than they are by who has above-marquee billing. If a movie looks good and it also happens to star Pitt, that’s a bonus. But if they’re not sure about whether to see a film that happens to feature a performance by Pitt, the actor’s presence probably isn’t going to tip the scale toward “go.”

Fortunately for Pitt — a Hollywood veteran who seems to have all the money and personal fulfillment one could possibly crave — he doesn’t have to worry much about the box office, at least not in this case. “Killing Them Softly” was a smaller, under-the-radar film that whiffed in a mostly small, under-the-radar way.

Now, if “World War Z” — a mega-big, potential blockbuster that opens smack in the middle of the summer 2013 season — opens with $7 million? Then, perhaps, Pitt will have something to worry about.

Because, per what was written two paragraphs prior, a movie about a zombie-pocalypse has built-in audience appeal. And a movie about a zombie-pocalypse with Brad Pitt . . . well, that theoretically should be an extra bonus.