Not since Mel Gibson has a superstar emphasized their buttocks onscreen as much as Jennifer Aniston. Smacked by Ben Stiller in Along Came Polly. Bared for Vince Vaughn in The Break-Up. Now, lightly squeezed by Steve Zahn in Management.

A gentle caress is as much grip that first-time writer-director Stephen Belber musters on this thin romantic-comedy story. Along comes folly to a theretofore charming, low-key romance once Zahn starts skydiving into pools, covering Bad Company and studying Buddhism to be the man he thinks Aniston wants him to be.

Management casts moon-eyed Michael J. Fox lookalike Zahn as Mike, a front-desk overnighter at his parents’ motel. Stuck in small-town Arizona, Mike is smitten when motel-artwork saleswoman Sue (Aniston) checks in while on a business trip. Digging out a dusty bottle of wine as a “gift for guests,” Mike strikes up conversation.

There’s amusing trepidation in Sue’s response, namely a facial expression suggesting, not irrationally, that Mike might kill her. Still, there is a naivete in Mike’s lack of romantic expectations to which she responds. He’s right, if awkward. Her butt does look good in those slacks. So she allows him to cup it and, later, indulges in a spontaneously randy romp with Mike in a storage room.

Sue is a blast of relatively big-city oxygen that skips town, but Mike wants more. Turning into a switched-sex, slightly tamer version of All About Steve’s sweet-stalker plot, Management puts Mike on the road to track down Sue. As annoying and mildly creepy as Mike seems to be, his earnest worldview begins to take hold with her.

Management offers occasional insights on how loners inadvertently back themselves into emotionally corners — underplayed with skill by Zahn and Aniston. Were Belber content to build on ideas Mike and Sue consider about life after meeting, it would be a slight, acceptable diversion.

But Management takes a hairpin turn into mainstream nuttiness, and the only impressive result is the introduction of Sue’s ex, Jango (Woody Harelson), an organic-yogurt magnate and “ex-punk.”

Harrelson gives the sort of comic performance Matthew McConaughey and, anymore, Owen Wilson, wish they could give — laconically breezy and a bit imposing. He has a one-liner about Joe Strummer that might be the funniest such quip all year.

Plus, in a brief role as a pawnbroker, Mark Boone Jr. officially enters the pantheon of always-reliable three-named character actors like Harry Dean Stanton and M. Emmett Walsh.

As in the similarly well-meaning Sunshine Cleaning, these performances are crowded out by too much quirk for quirk’s sake. Why the weird plot lapses into Kurt Cobain’s past and Vietnam War guilt? It’s too bad Management is ultimately unable to offer the same sort of reassuring pat as the one placed on Aniston’s behind.