ESPN has severed ties with a hard-hitting PBS "Frontline" documentary about the National Football League's management of player head injuries — a two-hour show that was a collaboration between the sports giant and the public television network.

The decision raises questions about whether the sports network yielded to pressure from the NFL, and highlights the delicate balance it must maintain with its billion-dollar partner.

ESPN asked Thursday to have its logos and credit removed from the "Frontline" episode, which includes interviews with former NFL players and is not expected to portray the league in a flattering light.

"League of Denial" began production more than a year ago as a PBS-ESPN collaboration, produced by Raney Aronson-Rath and David Fanning and featuring ESPN reporters Mark Fainaru-Wada and Steve Fainaru.

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The NFL declined to participate in the making of the show, which asks whether the league withheld from players information about the long-term health effects of football head injuries.

PBS and ESPN representatives touted the show at a TV industry press event earlier this summer. Executives from the cable network appeared with "Frontline" producers to preview and promote "League of Denial" at the semiannual Television Critics Assn. meeting held in Beverly Hills.

But ESPN this week said that because it did not produce or have editorial control over "League of Denial" it would be inappropriate to be associated with the episode.

"The use of ESPN's marks could incorrectly imply that we have editorial control," the company said.

The timing of ESPN's decision to abandon the "Frontline" project raised questions about why ESPN suddenly developed concerns about editorial control.

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"If they were getting pressure from the NFL, it would've been logical for ESPN to say, 'We're going to pull out of this,'" said Rick Burton, the David B. Falk professor of sport management at Syracuse University and former chief marketing officer for the U.S. Olympic Committee at the Beijing 2008 Summer Olympics.

"The role of sports journalism is getting grayer by the minute," said Paul Swangard, managing director of the Warsaw Sports Marketing Center at the University of Oregon. "It's a huge challenge for anyone in the business who is trying to be a good partner to the various sports leagues and also balancing issues of editorial control."

The NFL said it exerted no pressure on the sports network.

"It is not true that we pressured ESPN to pull out of the film," said NFL spokesman Greg Aiello.

ESPN President John Skipper defended ESPN's decision and said his network has not shied away from covering the issue of head trauma in the NFL.

"We have been leaders in reporting on the concussion issue, dating back to the mid-1990s," Skipper said. "Most recently, we aired a lengthy, thorough, well-reported segment on 'Outside the Lines.' We will continue to report this story."

ESPN, owned by Walt Disney Co., will pay the NFL about $1.1 billion for its "Monday Night Football" package this season. Next season, a new long-term contract begins that will raise the average price for ESPN to almost $2 billion per season for its NFL rights.

Also, the NFL is currently involved in hundreds of federal lawsuits involving more than 4,000 former players who contend the league hid what it knew about the possible long-term damage from playing the game.

"League of Denial" producers Aronson-Rath and Fanning said ESPN executives would have been shown the documentary before it aired and their input would have been taken into consideration during the final edits.

In a statement about ESPN's decision on Thursday, they said, "We regret ESPN's decision to end a collaboration that has spanned the last 15 months and is based on the work of ESPN reporters Mark Fainaru-Wada and Steve Fainaru, as well as 'Frontline's' own original journalism."

The producers did not speculate on the reasons for ESPN's withdrawal, but said, "We've been in synch on the goals of our reporting: to present the deepest accounting so far of the league's handling of questions around the long-term impact of concussions."

This is not the first time questions of league influence over its sports network partner have been raised.

A decade ago, ESPN aired "Playmakers," a dramatic scripted series about rogue members of a fictional football team. The league's top brass and some team owners were very critical of the series, which despite strong ratings was canceled after just one season.

Despite that, ESPN senior coordination producer Dwayne Bray said last month that the cable network's relationship with the NFL and other sports leagues doesn't factor into its journalism.

"ESPN is the gold standard for sports journalism, from covering the games to investigative journalism," Bray said, adding that the company "made a conscious decision when we were presented with this opportunity to literally get in bed with 'Frontline.'"

joe.flint@latimes.com

Times staff writers Meg James, Ryan Faughnder and Sam Farmer contributed to this report.