August is not too early to start the Oscar guessing game, especially when the Academy itself is already teasing big changes for next year.

A few days ago they breathlessly — and idiotically — announced the creation of a new award, for “achievement in popular film,” details to be hammered out later. It’s Hollywood admitting they make a lot of dumb movies that will never win awards — an admission that won’t sit well with people making popular movies that are actually smart.

The move also stems from panic about declining ratings for the Oscar telecast, allegedly because the audience hasn’t seen winners such as “Birdman” and “Spotlight” and “La La Land” (sorry, I meant “Moonlight”). If the idea goes forward, it will likely mean that a superhero picture like “Black Panther” is relegated to the kiddie table of “Best Popular Film,” instead of getting nominated for Best Picture, which it probably would have anyway.

You may be thinking, “Haven’t the Oscars always been absurd?” Well, sure. For instance, actors generally win not for giving the best performances, but the showiest.

This year an appropriately low-key sort of Oscar buzz is gathering around a genuinely deserving performance: Kelly Macdonald’s understated lead turn in “Puzzle.” The Scottish actress has bounced around agreeably since her 1996 debut in “Trainspotting.” She’s nailed the occasional supporting appearance in a big movie (“No Country for Old Men”) and doing duty on TV (“Boardwalk Empire”).

But this is the first time she’s ever really carried a film, and she’s frankly wonderful. Makes you wonder why her male “Trainspotting” co-leads seemed to leap easily into lead roles, while she was relegated to ensemble work. Or maybe you don’t wonder.

In “Puzzle,” Macdonald plays a housewife and mother, Agnes, whose suburban Connecticut life has grown humdrum without her even noticing. When someone gives her a jigsaw puzzle, it unlocks a previously unsuspected talent: Turns out Agnes has a Rainman-like ability to glance at a thousand puzzle pieces and assemble them in short order.

This leads to friendship with a philosophical puzzle-master (puckish “Life of Pi” star Irrfan Khan) and the awareness of a world beyond her modest household.

Director Marc Turtletaub breaks no new ground in this situation, but “Puzzle” has an admirably generous attitude, and a reluctance to designate villains. Agnes’s husband (David Denman, from “The Office”), for instance, is a well-meaning schlub who hasn’t evolved. But he’s not an ogre.

Maybe everything’s just a little too easy in “Puzzle,” but this movie’s quiet approach is welcome anyway. And it’s always great to see a talented actor own a movie after doing supporting service for so long; with her pinched face and tiny stature (she regularly vanishes within Agnes’ sweaters and jackets), Macdonald conveys a lifetime’s experience of fitting into other people’s plans.

This is a quiet process of personal emancipation, and a splashier performance would violate Agnes’ shy manner. Macdonald understands that completely.

Worthy of an Oscar nomination? You bet. But if “Most Popular” has become the mood, this appealing wallflower might not have a chance.

“Puzzle” (3 stars)

“Trainspotting” star Kelly Macdonald shines in her first true leading role, as a mousy housewife who discovers a genius for solving jigsaw puzzles. The revelation leads to a different kind of life, a story that might not be terribly new but is nicely handled here. Irrfan Khan co-stars as a champion puzzle-master.

Rating: R, for language

Opening Friday: SIFF Cinema Uptown