University of Missouri defensive end Michael Sam stands to make history as the first openly gay athlete in the National Football League. The league, sports media, and armchair commentators are now scrambling to predict how the All American’s disclosure of his sexual orientation may affect his future team members.

Though the public response to Sam’s announcement has been overwhelmingly positive, social psychology and organizational behavior research suggest he may have a struggle ahead. His success or failure in the NFL will largely depend on the leadership of his prospective team.

Sam’s Mizzou family supported him as an openly gay player, and he had an odds-defying season. But he began his career with the Tigers as a closeted gay man. That distinction is key. Anti-gay attitudes decrease when individuals have close gay friends, University of California, Davis psychologist Gregory Herek has found. Compared to other stigmatized groups, gay men and women have the advantage of concealing their stigmatized identity in new relationships — coming out once they’ve established trust. Because Sam’s sexual orientation will be known before he ever signs to a team, this opportunity to “win hearts, then change minds” may be lost.

Second, research on “implicit cognition” — the study of rapid and automatic psychological processes — has shown that most of us hold biases we aren’t aware of, and which can often contradict attitudes we express. Even when we hold strong values about fairness, studies have shown, these implicit biases reduce our friendliness to minority group members, decrease our ratings of minority service employees, and even affect our willingness to invite minority candidates for job interviews.

While we may want to treat others equally, these subconscious biases may still win out in the moment, because they influence the more spontaneous, visceral and emotional aspects of our decisions. Biases are stubborn things, even when we’re motivated to overcome them. Unfortunately, the NFL appears to have plenty of players unwilling to try — as demonstrated by Chris Culliver’s infamous anti-gay rant following last year’s Super Bowl.