Fox Networks Group will most likely not have a new ad-sales chief in place as it prepares to start TV’s “upfront” negotiations, according to five people with knowledge of the situation, leaving the company without a key executive during a critical industry period when haggling for billions of dollars of commercial inventory takes place.

The 21st Century Fox unit, which oversees the operations of Fox Broadcasting, FX, and Fox Sports 1, among other assets, parted ways with its last ad-sales head, Toby Byrne, in September of 2016. Byrne had helped set in place a new unified sales team that did deals for digital, cable and broadcast inventory; pushed for more agreements based on a seven-day viewing window; and unveiled an eyebrow-raising pact with Pepsi that put the soda giant into a plot line over three episodes of the hit drama “Empire.” Byrne and Fox could not come to terms on a new contract.

The search has been the talk of the advertising-sales community, as media buyers and Fox rivals mull who might or might not get the job – and when it might finally be filled.  Fox Networks declined to comment.

Fox Broadcasting secured between $1.47 billion and $1.64 billion in advance advertising commitments in last year’s upfront, according to Variety estimates, compared with between $1.43 billion and $1.56 billion in 2015.

Since the fall, Fox Networks has conducted a broad search for a successor – a long period, by industry standards. Michael Kassan, the chief executive of MediaLink, a strategic advisory firm overseeing the search process, said the company is eager to find an advertising guru who focuses less on TV ratings and more on bigger alliances and partnerships, while Randy Freer, president and chief operating officer of Fox Networks Group, continues to concentrate on generating revenue across a number of different areas.

“Revenue is no longer just about ad sales,” said Kassan, in an interview. “Randy Freer has been the person in charge of revenue, and there is continuity in place.” Kassan declined to specify a time frame for the executive search to be completed.

Over the months, the list of executives who are believed to have been considered included Adam Bain, the former chief operating officer of Twitter; David Lawenda, a former ad sales president at Univision and head of U.S. Global Solutions at Facebook; Sharon O’Sullivan, a former senior ad-sales executive at Discovery Communications; and Joe Uva, the former Univision Communications CEO.

One issue at play, according to several people familiar with the process, is that a new entrant might have to share responsibilities with others. Both Freer and Joe Marchese, president of advanced advertising at Fox Networks Group, have a strong hand in certain aspects of advertising outreach.

Indeed, Marchese, who has long been viewed as a potential internal candidate for the post, has taken a more public role in recent weeks. He has represented Fox Networks in a new effort called “Open A.P.,” that seeks to give advertisers a better way to buy advertising aimed at groups of consumers more narrowly defined than the norm. Viacom and Time Warner’s Turner are also taking part in the venture – a rare instance of media competitors cooperating with each other.

In the absence of a new ad-sales chief, Freer and Marchese are likely to lead a mid-May upfront presentation of new Fox programming to advertisers, along with Dana Walden and Gary Newman, co-chairman of Fox Television Group, according to people familiar with the situation. Bruce Lefkowitz, an executive vice president of ad sales for Fox Networks, is expected to continue shouldering oversight of day-to-day ad-sales operations, though he is not believed to be a candidate at present for the senior job.

One media-buying executive suggested Fox’s prolonged process has left Madison Avenue somewhat confused. Someone needs to marshal ad-sales forces across multiple networks, this executive said, and serve as a designated point person for advertisers. “I don’t understand why Toby isn’t there,” this executive said.