When he was running ABC Entertainment, Disney Chairman Robert Iger raised eyebrows by speculating that TV economics might eventually compel the major networks to pare their primetime lineups from 22 hours a week to 15 or less.

While Iger has ascended the corporate ladder in the intervening 15 years, his observation is quietly becoming prescient. Because like Disneyland’s old “Adventure Thru Inner Space” ride, network programming is slowly, inexorably shrinking — a trend that could be hastened by the time-shifting technology popularized by digital video recorders such as TiVo.

Desperate to contain costs, networks have found that one way to reduce their overhead is simply to vacate hours previously earmarked for original fare. As a consequence, Saturday has essentially disappeared from the week, as ABC, CBS and NBC use the night either for primetime sports or as Rerun Theater.

NBC, meanwhile, took advantage of acquiring NFL football to obliterate Sunday nights throughout the fall, airing an extended pregame show (part of which runs ad-free, and thus unrated) before each game, encompassing four hours. Considering ABC’s “Monday Night Football” usually kicked off at 9 p.m. Eastern time, the NBC Sunday version conveniently knocks another two hours out of the net’s primetime week.

Based on the networks’ body language, Friday could be the next parcel of real estate in jeopardy of foreclosure. CBS research guru David Poltrack has pointed to the high volume of DVR playback occurring that night, and depressed ratings could lead to more reruns there, as ABC did most of last season with encore plays of “Grey’s Anatomy.” Fortunately, the Alphabet web’s new Friday drama “Women’s Murder Club” got off to a promising start, which could help provide a temporary stay of execution.

Networks have been even more aggressive in finding ways to reduce their investment in other dayparts by stretching “Today” to occupy a fourth hour or brokering their entire Saturday-morning lineups to outside suppliers — the same arena, by the way, that once yielded the enormously lucrative “Teenage Mutant Ninja Turtles” and “Mighty Morphin Power Rangers,” the latter transforming Haim Saban from a “cartoon schlepper,” as he was fond of calling himself, into a billionaire investor.

Once sacrosanct, primetime no longer seems off limits to such deals, shedding hours by saying “Here, gimme some money for the space, and Saturdays from 8 to 10 can be your problem.”

Other inexpensive ways to fill time — such as stripping talk- or gameshows in primetime Monday through Friday — aren’t farfetched either. Indeed, with Jay Leno’s post-2009 plans mired in uncertainty, somebody could easily try relocating a latenight personality to an earlier hour, given that the 5.8 million people watching “The Tonight Show” on average (at an hour when far fewer sets are in use) exceeds the audience for anything on the CW network.

Of course, by sacrificing shelf space, the networks could be guilty of penny-wise and pound-foolish behavior, inasmuch as nobody can guess where they’ll find the next hit. Although Saturday and Friday look relatively moribund, you don’t have to go back to “All in the Family” to find stalwarts introduced in weekend slots, lest anybody forget that “CSI” and before that “The X-Files” both made their debut on Friday en route to becoming hugely bountiful properties.

On a separate front, throwing in the towel on struggling time periods represents bad news for the talent guilds, which despite an infusion of fresh cable series are losing out on hours once allocated to television’s highest-paying and most prestigious programs. Take NBC, which between football, reruns, newsmags, reality and gameshows devotes only half of its 22 hours to firstrun scripted fare.

Last week, at a more-ho-hum-than-usual Hollywood Radio & Television Society summit of the network entertainment chiefs, Fox Entertainment Prexy Kevin Reilly alluded to the delicate balancing act broadcasters face given their besieged and rapidly evolving economic model.

“We are at an inflection point in the business where things are really shifting,” he said.

Nobody knows where the bouncing ball will wind up, which is at the root of the town’s labor woes. Yet even as those negotiations continue, the networks are already hedging their bets by gradually whittling away at their commitment to TV programming — cutting their possible losses even as they simultaneously blunt their potential upsides, one rerun and football game at a time.