HBO's seminal series Game of Thrones came to an end this summer under the purview of John Stankey, the AT&T executive currently in charge of the WarnerMedia entertainment division of AT&T. Now, though, Stankey could be playing his own version of the game in a bid to take over AT&T's Communications division -- a move that would give him oversight of a much larger operation and one that could put him in line to eventually take over the top spot from AT&T CEO Randall Stephenson.

But, according to Recon Analytics Founder Roger Entner, Stankey is likely to face serious challenges from several other top AT&T executives, including Jeff McElfresh and Lori Lee.

As winter slowly makes it way towards AT&T's Dallas headquarters, Entner has some advice for all the candidates angling for Stephenson's ear: "You should never underestimate John Stankey."

Chaos is a ladder
This week, AT&T's John Donovan surprised the telecommunications industry with the announcement that he would retire in October, essentially vacating the throne sitting atop what is by far AT&T's biggest business. As Bloomberg recently pointed out, AT&T's Communications division generated 77% of the overall company's revenue in its most recent quarter, and 84% of its profit. Thus, there's little doubt that the executive who wins the leadership position at AT&T Communications would be top choice to eventually lead all of AT&T.

And that may also be why Donovan is retiring. At 58, Donovan is the same age as Stephenson and may have decided there was little chance for him to succeed Stephenson, who has shown no desire to relinquish his post.

Thus, Donovan's departure sets up a real-life Game of Thrones scenario at the company that purchased the rights to the fictional TV series, along with everything else owned by Time Warner, in an $85 billion transaction that officially closed last year.

Hold the door!
As Bloomberg reported, AT&T's Lori Lee -- currently chief of AT&T's Latin American business and reporting directly to Stephenson -- is widely viewed as a leading contender to replace Donovan. "She would be an excellent pick," acknowledged Susan Welsh de Grimaldo of Strategy Analytics.

But Entner argued that McElfresh is likely also in the running, given his rapid ascension to the top spot in AT&T's Technology and Operations unit, the operation in charge of much of AT&T's networking efforts, including 5G. Donovan moved him there last year shortly after AT&T closed its acquisition of Time Warner. As part of that action, Donovan himself was named as head of AT&T Communications while Lee took over the Latin American business. Brian Lesser was brought in from GroupM to head up AT&T's advertising and analytics business called Xandr, and Stankey was put in charge of the WarnerMedia division that houses AT&T's entertainment businesses that stretch from HBO to DirecTV.

McElfresh is a 21-year veteran of AT&T and most recently served as the head of AT&T's Vrio business.

AT&T also has a long corporate history of grooming internal candidates for leadership positions. Other executives that analysts have fingered as possibilities for replacing Donovan include:

Other prominent executives in AT&T's networking division, such as Igal Elbaz or Chris Penrose, are viewed as unready for such a senior leadership role.

Beyond Westeros
Stephenson and AT&T's board of directors may also be considering external candidates. Such a move has precedence, considering Verizon's Lowell McAdam hired Ericsson's former CEO, Hans Vestberg, as Verizon's CTO in an effort to inject some new blood into the company. And Vestberg is now Verizon's CEO.

Stephenson could look to AT&T's own networking vendors like Ericsson or Cisco Systems for possible candidates to replace Donovan.

Or, as Mark Lowenstein of Mobile Ecosystem pointed out, the proposed merger between Sprint and T-Mobile could ultimately shed executives with the networking chops to replace Donovan. Some reports have indicated that T-Mobile's COO Mike Sievert will take over leadership of the combined company, if that transaction is ultimately approved by regulators. Such actions could free up executives like Sprint's John Saw or T-Mobile's Mark McDiarmid for the position at AT&T.

— Mike Dano, Editorial Director, 5G & Mobile Strategies, Light Reading | @mikeddano