If you were ever curious about how Dan Duquette discovered and rescued Tim Wakefield from the scrap heap ? if you ever wondered how baseball GMs pick through that scrap heap in general ? then go see “Moneyball.”Just don’t expect to get too detailed an explanation of how the process works.”Moneyball” is based on author Michael Lewis’ book of the same name and features Brad Pitt in the starring role of Oakland A’s GM Billy Beane ? who became famous doing the same kind of work Duquette and, later, Theo Epstein did in Boston.The reason for their efforts can be summed up in three words: New York Yankees. We see them snatch one of the A’s best players, Jason Giambi, as the movie begins. (Alas, the Red Sox are portrayed as an Evil Empire too, with the Duke shown scooping up Johnny Damon.) Because the George Steinbrenners of the world can buy their way to a championship, small-market teams like the A’s are relegated to the basement of the American League.”Moneyball” shows how Beane gets out of the basement through a Filene’s Basement approach: Finding value in the undervalued. In the film’s promising first half, we see how Beane gradually embraces this approach, thanks to the unlikeliest of assistants, a Yale grad with an economics degree named Peter Brand (Jonah Hill). We see Beane stun his supposedly savvy scouts, and his manager Art Howe (Philip Seymour Hoffman), with his choices to fill the voids left by Giambi, Damon and company ? replacements like Jason’s younger brother Jeremy Giambi, ex-catcher Scott Hatteberg, and unusual-throwing reliever Chad Bradford. (All three, incidentally, are former Red Sox players.)Yet the trouble is, I went into the Somerville Theater without a clear understanding of how sabermetrics works ? and I left pretty much the same way. Director Bennett Miller, and writers Aaron Sorkin and Steven Zaillian, have treated sabermetrics as some kind of arcane knowledge straight out of “The Da Vinci Code,” best explained by mystic digits flashing on a screen. We see the philosophy of Bill James basically reduced to a simple stat, on-base percentage, yet we rarely see the A’s hit with men on base ? indeed, the biggest hit of the film is Hattie’s walk-off solo home run to clinch a 20-game win streak.That’s too bad, because moviegoers might wonder, how is it possible to outsmart opponents who outspend you by hundreds of millions of dollars. How was, for instance, Duquette able to see the value in a washed-up knuckleballer who had been released by the Pittsburgh Pirates in 1995 ? and how was Epstein able to see the value of exchanging the face of the franchise, Nomar Garciaparra, for a trio of decent-but-hardly-star-power players in Orlando Cabrera, Doug Mientkiewicz and Dave Roberts in 2004? (Theo, it appears, forgot those lessons this year.)There is much to like about “Moneyball” ? Pitt, Hill, Hoffman, newcomer Kerris Dorsey as Beane’s guitar-playing young daughter Casey. Red Sox fans will take interest when John Henry (Arliss Howard) offers the Boston GM job to Beane on a rainy day at Fenway Park and the film notes that while Beane turned it down, the Sox did win their first World Series in 86 years using sabermetric concepts.It’s just too bad that, where the movie could have hit the cinematic equivalent of a home run, it settled for a ground-rule double.Rich Tenorio is The Item’s sports copy editor.