On Sunday, ESPN.com reported that Davis was injured during a recent post-practice period for extra work when he was hit by a Browns linebacker. According to the report, witnesses said Davis was not wearing shoulder pads while the unidentified defender who hit him had them on.
League spokesman Greg Aiello said the league is aware of the alleged incident and has been looking into the matter.
"The review is ongoing," Aiello said in an e-mail response to The Associated Press.
Mangini confirmed Monday that he has had discussions with the league, and said that following his own research that he's "comfortable with where we are on it."
"I like James Davis a lot," Mangini said. "The last thing we want to do is ever put him in a position or anybody in a position where they could get hurt. I've talked to a lot of people involved in it and we're going to continue to work with the league on it."
Mangini did not deny the report, but repeated several times that he has been in touch with the league.
He said the post-practice period is open to all players to get in extra work, but that it's normally attended by rookies and younger players. He said the workouts are done in a controlled environment, supervised by coaches. Mangini said he occasionally watches.
Mangini noted that Patriots quarterback Tom Brady took part in similar sessions during his first season with New England.
Mangini said he would never condone a situation like the one being reported.
"We'd never do that," he said. "If something like that did happen, it shouldn't happen. Ever."
A sixth-round draft pick from Clemson, Davis was impressive in training camp and the exhibition season. He was hurt in the season opener against Minnesota and was placed on injured reserve on Oct. 3.
The ESPN report said the NFL Players Association may file a grievance, although Davis may hesitate for fear of losing his job. His base salary is $310,000 this season.
Browns linebacker D'Qwell Jackson did not see the incident, and thought it sounded implausible. He said players can be fined by Mangini for not wearing the proper pads at practice.
"That sounds crazy to me that something like that would be reported," Jackson said. "But I wasn't there. I don't know exactly what happened. That doesn't make any sense to me. That wouldn't be fair to him [Davis]."
Running back Jamal Lewis, who knows Davis well, avoided any specific questions about the incident.
"Actually, I don't really know none of that," said Lewis, who attended the same Atlanta high school as Davis. "I just know that he had hurt his shoulder in the first game. That's all I really know about."
Mangini confirmed that Davis will need surgery but would not say if an operation has been scheduled.