If the NFL intends to sue The New York Times for its recent exposé of the league's concussion research, it better be prepared for a tough slog.

On Monday, the NFL sent a letter to The New York Times demanding that the newspaper retract a recent front-page story that called into question concussion analysis that the league has stood by for years.

The letter, addressed to an attorney for The New York Times, calls the newspaper's article "false and defamatory." It also appears to hint at the possibility of legal action, requesting that the paper's journalists save the notes that accumulated in the course of their reporting.

But The New York Times shows no sign of backing down. In a letter sent to the NFL Wednesday, the Gray Lady outlined a scathing rebuttal, noting that the league's grievance only "confirms the overarching point" of its exposé.

The NFL would likely be hard-pressed to prevail in any legal battle involving libel against The New York Times owing to a precedent that the Times itself helped bring about in a 1964 case against Montgomery Public Safety commissioner L. B. Sullivan. The ruling in that matter, New York Times v. Sullivan, established the "actual malice" standard for plaintiffs bringing libel lawsuits against the press, which states that public figures must be able to prove a news organization demonstrated a "reckless disregard for the truth" to win their cases.

Three legal experts reached by Poynter Wednesday agree: Surmounting that legal barrier would be a daunting, though not impossible, task for the NFL.

"Short of having somebody on the phone saying ‘I’m going to get you and your little dog, too,’ it’s always a fight,” said Scott Greenfield, a lawyer in New York who is the managing editor of the online legal magazine Fault Lines.

But the NFL's request that reporters save their notes is an indicator that the league is considering mounting a legal offensive with the intent to prove malice, said Kevin Goldberg, a First Amendment attorney at legal firm Fletcher, Heald & Hildreth. Malice is difficult to prove, and a close look at the reporters' notebooks is one of the limited ways to demonstrate Times reporters could have purposely ignored the facts.

"They're basically saying to The New York Times: We think that you acted with knowledge that the statements were false..." Goldberg said. "And a lot of that is going to be based on the mindset of those who worked on this article. So we need your notes, we need your background materials, everything else to have you put that story together."

The letter comes on the heels of a 2,500-word rejoinder issued by the NFL to The New York Times claiming that the newspaper misstated the league's connection to the tobacco industry, which it called "odious" in the newspaper's story. The Times, for its part, has repeatedly and publicly stood by its reporting, on Twitter and in a formal statement, and says that the NFL has yet to find fault with any of the facts in the story.

When reached for comment, the NFL referred Poynter to its grievance letter. The Times reiterated a defense of its reporting previously published by POLITICO.

"We see no reason to retract anything," said New York Times sports editor Jason Stallman. "The N.F.L. apparently objects to our reporting that the league had ties to the tobacco industry. But, as the article noted, a co-owner of the Giants, Preston R. Tisch, also partly owned a leading cigarette company, Lorillard, and was a board member of both the Tobacco Institute and the Council for Tobacco Research, two entities that played a central role in misusing science to hide the risks of cigarettes. Also, the N.F.L. and the tobacco industry shared lobbyists, lawyers and consultants."

If the NFL decides to sue The New York Times, the league might try to make its case by convincing the court that the newspaper exaggerated its ties to the tobacco industry, Greenfield said. If a jury finds the connection tenuous, they may give credence to NFL's argument.

Even if the NFL prevails in its case against the Times, it may be hard for the league to demonstrate that its reputation has been significantly harmed by the newspaper's story, Goldberg said. The NFL's fraught relationship with concussions and player safety is no secret, both having being dramatized recently in a blockbuster movie starring Will Smith. This could prevent the NFL from inflicting hefty monetary damage against The New York Times in the event that a jury rules against the newspaper.

But the fact that the NFL is taking formal steps to catalog its grievances with The New York Times is an indicator that the league is serious about taking the matter further, Goldberg said. By raising the specter of a lawsuit, the league would also be opening itself to scrutiny for the duration of the case — another signal that it's serious about fighting the story.

"That's the reason a lot of savvy corporations and public figures don't bring lawsuits," Goldberg said. "Not because they won't win. It's that the resulting litigation will bring things out that've never been out before."

It's also possible the NFL may be bluffing in order to intimidate news organizations who would otherwise publish damning stories about the league, Goldberg said. Whatever the case, the league is at the foot of an uphill battle.

"(Actual malice) is a high standard, and it's quite often one that sets the odds for who's going to win," Goldberg said. "It's very hard for someone to win when they have to prove actual malice."

Mary Anne Franks, a law professor at the University of Miami, agreed.

"The 'actual malice' standard is generally considered to be a high bar, as imposing liability for errors or speculation in media reporting runs the risk of chilling the media's willingness and ability to openly engage in discourse on matters of public concern."