ESPN President John Skipper released a statement Friday defending the network's journalistic integrity after it pulled out of an investigation of the NFL.

ESPN had been a partner with PBS's Frontlineon a forthcoming series about concussions in the National Football League. A trailer for the two-part investigation says Frontline"investigates what the NFL knew and when they knew it" regarding the lasting effects of head injuries.

But Thursday, word broke that ESPN asked for its branding and credits to be removed on all "League of Denial" content.

PBS released a statement saying it regretted ESPN's decision "to end a collaboration that has spanned the last 15 months."

Friday, Skipper pledged to "continue to report this story and continue to support the work of Mark Fainaru-Wada and Steve Fainaru," two ESPN reporters who are writing a book on brain injuries and collaborated with the Frontline team.

"Is ESPN trying to have its cake and eat it too here? Let's just say it'll be interesting to see whether it promotes its reporters' book and reports on the Frontline documentary or if it backs away," sportswriter Stefan Fatsis tells NPR's Audie Cornish on All Things Considered.

Fatsis knows the two sports reporters professionally and says the fact that they work for ESPN "is a credit to the company's journalistic ambitions." Mark Fainaru-Wada has covered steroid use extensively and his brother, Steve Fainaru, won a Pulitzer Prize in 2008 for international reporting.

"But ESPN has this other side — its relationship with the leagues," Fatsis says, "and it looks as if that's what finally tripped up the project."

He says ESPN pays the NFL more than $1 billion annually to broadcast Monday Night Football. The New York Times reports that the NFL pressured the network to back out of its partnership with Frontline, citing "two people with direct knowledge of the situation." The Times adds:

"ESPN's role came under intense pressure by the league, the two people said, after a trailer for the documentary was released Aug. 6, the day that the project was discussed at a Television Critics Association event in Beverly Hills, Calif."

Citing its unnamed sources, the Times reports that league officials "conveyed their displeasure with the direction of the documentary" in a lunch meeting last week with Skipper and ESPN's vice president for production, John Wildhack.

NFL spokesman Greg Aiello told the Times Friday that the lunch was arranged weeks ago and that "at no time did we formally or informally ask them to divorce themselves from the project."

ESPN said it withdrew from the project because of lack of editorial control, but Frontlinedeputy executive producer Raney Aronson-Rath told The New York Times the "ground rules of the collaboration" had been solidified for "more than a year."

Derek Thompson, senior editor for The Atlantic, told WBUR's Here and Now on Friday that ESPN's withdrawal may have some unintended consequences.

"Ironically, by creating a tremendous controversy over this Frontlinedocumentary on head injuries, this documentary's gonna be seen by ... vastly more people than it would have otherwise," he said. "So the NFL and ESPN to a certain extent have ironically given this doc the best possible publicity it could receive."

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