Doctors that work for professional football teams have conflicts of interest that could jeopardize players’ health, according to a report by Harvard researchers.

The report released Thursday, funded by the NFL players’ union, states that because doctors are paid by the teams, they may put teams’ business above players’ health interests. However, it doesn’t identify any specific instances when this has occurred.

League sources flatly denied the existence of any such conflict of interest, calling the report nothing more than an academic exercise.

Currently, NFL teams pay a cadre of medical staff to care for players on and off the field. Physicians and athletic trainers help decide when to pull players out and when to put them back in. Since those doctors and athletic trainers are hired and fired by the teams, they may make decisions in the interest of the team that are not in the interest of the players, the report states.

“[Players] are treated by people who are well-meaning, don’t get me wrong, but operate in a structure that’s infected with a structural conflict of interest,” said I. Glenn Cohen, a Harvard Law School professor who coauthored the report. “That conflict of interest is that they serve two people — they serve the player and the serve the [team].”

The report quotes an unnamed player who says that some players don’t trust doctors because they work for the team. Coauthor and Harvard Medical School professor Holly Fernandez Lynch said investigating individual instances of jeopardized decision-making fell outside of the scope of the report.

In a letter responding to the report, the NFL provided quotes from named players attesting to the integrity of the medical process.

The report recommends that the NFL and the union create a committee to make decisions about the hiring, firing, and compensation of most team medical personnel. The league and union would appoint members of the committee, and the doctors and trainers would still be paid by the teams. Teams would also be allowed to hire one additional doctor to advise them on business decisions, but who would not treat players.

The report was part of the Football Players Health Study, a wide-ranging initiative at Harvard funded by the union.

Independent legal and ethical researchers said it’s a step in the right direction — but a former NFL doctor thinks it’s a bad idea.

Dr. Christopher Wahl, who served as the head team physician for the San Diego Chargers from 2013 through 2015 and currently has no relationship with the NFL, said that he “never once got any pressure to play an injured player” and that this recommendation “is trying to solve a problem that is largely nonexistent.”

“While I think you can’t deny there are theoretical conflicts of interest, there’s no motivation for physicians to do the wrong thing for players,” Wahl said.

The NFL said that players already have the right to seek a second opinion from a doctor of their choosing, for which the team covers the costs.

In preparing this report, researchers reviewed scientific and legal literature, popular media reports, and documents from the league and the union; they also spoke with current and former players, players’ advisers, family members, legal experts, and league and union officials.

They did not speak with current team doctors — Cohen said that the team asked the NFL multiple times for these interviews, but was denied each time.

The NFL did contribute to the report, however, including reviewing a draft, providing dozens of pages of comments, and writing a letter that will be published along with the report.

In that letter, the league listed the many ways in which it works together with the union to provide top-notch medical care to its players, and characterized the Harvard report as an “inherently flawed and unreliable assessment” whose main recommendation would have an “extremely detrimental” impact on the care of players.

Dr. Steven Joffe, vice chair of medical ethics at the Perelman School of Medicine at the University of Pennsylvania, described the NFL’s response as “frankly terrifying.”

“It’s so obvious that there’s a conflict of interest,” Joffe said. “The fact that the NFL and the NFL Physicians Society would deny it is to me the biggest flag in this whole report that there’s a serious problem here that needs to get fixed.”

Wahl said the main recommendation would do more harm than good. Knowing how likely a team is to keep a player helps doctors better discuss potential risks with players. And the team physician can serve as an advocate for the players in discussions with team management—if an injured player feels like they should play anyway, for fear of being cut, the team doctor, who understands the player’s predicament, can take responsibility for the decision and advocate for the player to sit out but stay on the team, he said.

Scholars in the field say that Harvard’s recommendation is a good idea, but not a new one.

“These are things that I’ve been saying for at least the last decade,” said Steve Calandrillo, a professor at the University of Washington School of Law. In 2006, he published an academic paper with a similar recommendation, but it attracted little attention from the media or the NFL.

Tom Talavage, a neurotrauma researcher at Purdue University, said that he has been involved in discussions about making a similar change at a college level for athletic trainers. Athletic trainers are usually part of the athletic department, but should be part of an academic department, he said, so that the athletic director can’t fire them in retribution for keeping a player out.

League sources said that the changes to medical staff structure described in the Harvard report have never come up in discussion with the union.

The union said that it was too early to comment on the recommendations directly, but that it has generally supported disentangling doctors who treat players from the NFL business complex, with, for example, the addition of unaffiliated experts to help identify concussions at games.

Any changes to policy would have to be formally adopted by the league and the union.

An NFL spokesperson said that the league “[looks] forward to studying [the report] in more detail and discussing the recommendations with our clubs, team medical staffs, and the [union].”

Bob Tedeschi contributed reporting.

Republished with permission from STAT. This article originally appeared on November 17, 2016