There will probably never be a big-screen Friends movie, but Run, Fat Boy, Run might be as close as we ever get. Directed by the sitcom’s star David Schwimmer, it has about the same amount of jokes, which are all uniformly predictable, and the same barely sketched-out characters who get in vaguely dangerous but never threatening situations. The story follows the arc you want it to with absolutely no diversions, and the end is satisfying if entirely forgettable. That works for a half-hour sitcom, but at feature length, the formula wears out its welcome.

The screenplay is shockingly by-the-numbers, given that it is written by Michael Ian Black and Simon Pegg, two writer-actors who have perfected offbeat humor (Black in TV’s “The State” and Wet Hot American Summer, Pegg in the glorious Shaun of the Dead and Hot Fuzz). Pegg plays Dennis, a Londoner still recovering from the huge mistake he made five years earlier, leaving his pregnant fiancée (Thandie Newton) at the altar. She’s now involved with smarmy hedge fund manager Whit (Hank Azaria), and in order to prove he’s worth coming back to, Dennis devises a scheme to run the London marathon. With the help of his layabout friend Gordon (Dylan Moran), who has made a huge bet on Dennis completing the race, and his landlord (Harish Patel), Dennis trains poorly, tries to give up several times, and never achieves anything close to the physique you’d expect from a marathoner.

No matter. This is movie logic we’re working with here, where running a marathon is enough to win back your ex-fiancée and no actual tragedy can occur, because hey, it’s a comedy! Whit, of course, is in the race as well, and even though Dennis sleeps in the morning it starts and barely looks like he can walk down the block, the two are neck-and-neck throughout the race. After Whit shows his true colors thanks to some dirty tricks, Dennis finally gets the chance to prove his dedication…to running. Whether or not he’ll be a decent husband is just left as subtext.

Pegg has perfected the role of the lovable slacker and coasts on it here, essentially reviving his Shaun of the Dead character but a bit emptier without collaborator Nick Frost to bounce off. Newton is utterly improbable as his ex-fiancée, and you can’t shake the feeling that she deserves better, even after Dennis goes out of his way to win her back. And Azaria is criminally wasted in what’s essentially a straight villain role. In a better and more original comedy, he and Pegg would be a formidable comedic team, but here he does little more than flex his impressive muscles and scowl.

In the end, Schwimmer just doesn’t have the directorial wit to elevate the intermittently amusing script, and none of the cast seems dedicated enough to raise the bar either. Run, Fat Boy, Run was a huge hit in the U.K., indicating that it’s not just Americans with an appetite for mediocrity. Given that Pegg, Newton and Azaria aren’t big enough stars over here, though, this country will likely be the one with enough sense to let this dud run away.