The NFL has been rocked by the news that some players have died of heart problems while playing in the league.
The Associated Press has reported that 11 players have already died of the disease.
It was first reported by ESPN’s Adam Schefter, who tweeted a screenshot of an NFL game from Sunday night.
Many fans have expressed anger and frustration on social media, but the NFL has not issued any official statement.
“Our thoughts and prayers are with those affected by this terrible tragedy,” a league spokesperson said in a statement.
The statement added: “As we always strive to be the most compassionate and fair organization, we are not commenting further at this time.”
Fans were also concerned about a recent study that found players who played in the NFL were more likely than those who did not to suffer from depression.
The AP says the study, conducted by the National Institute of Mental Health, found that more than 30 percent of those who played the NFL reported experiencing depression at least once a month.
The study is the first to look at the relationship between the frequency of depression in players and how they play the game.
The NFL, meanwhile, has said that it is aware of the findings, but it is not investigating the study.