Actors Kit Harington and Rose Leslie attend the Season 7 premiere of HBO's "Game of Thrones" in Los Angeles in 2017. (Neilson Barnard/Getty Images)

There’s a good chance you’ve never heard of Robert Greenblatt. But if you’re a consumer of quality television, Greenblatt could soon have a big effect on your life. At least your entertainment life.

Greenblatt is a longtime leader of NBC, Showtime and his own production company. He sits atop the list of people who could be brought in to run content at HBO now that its chief executive, Richard Plepler, will be leaving. The Turner Broadcasting portfolio of TNT and TBS, along with other WarnerMedia TV properties, would probably be in his purview as well.

Whether Greenblatt is hired — and how he handles (and is given authority to handle) the job when he has it — will have major consequences for the television landscape.

On Thursday, WarnerMedia owner AT&T announced Plepler, who has served as the chief executive of HBO for more than a decade, would be leaving the company.

This was not an idle game of media musical chairs (or thrones). That’s true for one simple reason: It’s likely Plepler won’t be fully replaced.

The existence of a chief executive at HBO was part of a very specific corporate tradition in which the company operated as a largely independent entity under former owner Time Warner, which mandated financial targets but didn’t, as a general rule, dictate business decisions. The fact that Plepler’s job existed meant HBO could make its own choices as a company — it could decide what shows to make, how often to make them and where to put them.

Plepler occupied a particular and in some ways endangered role at the country’s conglomerate-owned content firms — a kind of linchpin between the massive corporations that own them and the creative people who make them run. He was the reason HBO was free to pursue the paths its executives — and only its executives — saw fit.

Or put another way, he’s exactly the kind of executive a boss such as AT&T doesn’t have much of an interest in as it seeks to take greater control over the operation.

John Stankey, the AT&T veteran who is now the head of WarnerMedia, saluted the exiting Plepler. “Richard is one of the most successful executives in our industry and I have been fortunate to have his support over the last months,” he said in a statement. “His vision, energy and passion helped to elevate HBO’s brand to what it has become today.”

Plepler told employees in a memo that “it is the right time” to leave the company.

The big question is what happens next. And that’s where things get dicey.

The Plepler news came the same day that another lower-profile but equally consequential move was made by AT&T: David Levy, the longtime head of Turner Broadcasting, is also departing. Levy was in a position similar to Plepler’s and would be undergoing a similar fate. (Kevin Reilly, former TNT and TBS president, has already been in a new gig running WarnerMedia’s streaming service.) If Greenblatt comes in, the former NBC chief would probably be handed oversight of both of their buckets — at least on the content side — with the business side residing separately under AT&T.

Let’s clear one thing up. The narrative of an AT&T creative takeover, in which a Texas-based telco is now making decisions on the shows of one of the most prestigious networks around, would be too simplistic. The fact that an accomplished personality such as Greenblatt is being considered for the role suggests that HBO, network of “Game of Thrones,” and TNT/TBS, networks respectively of “The Alienist” and “Search Party,” will stay firmly within the realms of traditional television.

But will they stay within the bounds of what they’ve been doing? That part’s much less clear. And it’s Greenblatt and his new role that could spell the difference.

At the moment, Casey Bloys, who runs programming at HBO and has been shepherding “Thrones,” “Veep,” “Barry” and other high-end shows the past number of years, remains in his job. His fate could be announced in the coming days. If he stays, expect HBO to remain in key content respects largely as it is, maybe with just more of the same. (Bloys has already been given an added production budget for this year as the company tries to keep up with, or stay a reasonable distance behind, Netflix’s prodigious output.)

If Bloys joins Plepler out the door in the new AT&T structure, with Greenblatt being hired to assume more control, the potential outcomes are more nebulous.

Greenblatt has a history of making high-end television when given the latitude. As Showtime chief, he was behind shows such as “Dexter” and “Weeds” (both of which could have been on HBO), and as a producer, he was responsible for “Six Feet Under” (which was on HBO).

He also has been interested in, and shown a flair for, finding upscale mainstream hits. At NBC, he was behind “This Is Us” and “The Good Place” (shows that might plausibly have been on present-day TNT). And he has been behind less-upscale mainstream hits such as “The Voice” and the new “Will & Grace” (shows that don’t fit as neatly on the current HBO-TNT-TBS axis.)

One reasonable scenario for his new role would be for Greenblatt to reach into different parts of his past and oversee each property accordingly — serving HBO with the prestige side of his brain while trying to refashion TNT-TBS into a new NBC.

But that’s just one scenario. As HBO tries to up its content volume, it could mean that he or whoever gets the job, at the behest of AT&T, pushes for a broader and less pedigreed kind of programming at the network: Shows that might have been turned away from HBO are now included on it. Shows that currently define HBO take a less central role.

Not insignificant in this calculation is that HBO is already at a crossroads, with “Game of Thrones” about to end after its upcoming season debuts this spring. “Veep” is set to end, too. If you’re going to reshuffle HBO, this would be a good time to do it.

Key to all this, too, is the streaming service Reilly is running. Like Disney, AT&T is intent on making WarnerMedia a direct-to-consumer play. HBO’s content — indeed, Greenblatt’s potential mandate — could involve shows that best serve those needs. And how much of HBO’s current prestige programming fits with that goal is unclear.

Where Greenblatt and Reilly, incidentally, would stand relative to each other on the corporate organization chart — and thus where HBO and streaming fit in with each other — would be unclear, too.

But one thing is clear. HBO’s status as a stand-alone company within a conglomerate universe is becoming a vestige of the past. Whether the new iteration will resemble the old one could depend on the rules of a new media universe, AT&T and Bob Greenblatt.