In the NFL, when a Christian player sinks to the ground after a touchdown and praises god, that's prayer, and is not penalized under the League's rule against "going to the ground" in celebration after a play. But, apparently, Muslim players should think twice before trying to take advantage of the same rule.

Last night, Husain Abdullah, who plays safety for the Kansas City Chiefs, scored a touchdown. It was, presumably, a big moment for him. After he scored, Abdullah, a practicing Muslim, briefly sank to his knees and tapped his forehead to the ground in an instantly recognizable gesture of Muslim prayer.

But to the referee, it was "unsportsmanlike conduct." He gave Abdullah a 15-yard penalty for excessive celebration.

As SB Nation points out, the NFL does have a rule against "going to the ground" in celebration of a touchdown. But when Christian players take a knee and have a moment of religious thanks after they score, their celebration is not deemed to be "excessive." Indeed, the famously devout former NFL quarterback Tim Tebow did that so often that his one-kneed prayer gesture became known as "Tebowing," a word that he successfully trademarked in 2012.

This is manifestly unfair. Abdullah, like Tebow, is known for his devotion to his faith. Abdullah missed the entire 2012 NFL season so that he could undertake a pilgrimage to Mecca, and he fasts during Ramadan, which means he cannot eat food or drink water during daylight hours for a month, despite his grueling NFL training schedule. And yet Tebow's prayer during games earned him respect, but Abdullah's earned him punishment.

The NFL has admitted that the referee was wrong to penalize Abdullah. NFL spokesman Michael Signora wrote in an email to USA Today that, although there is a rule against players engaging in celebration while on the ground, "the officiating mechanic in this situation is not to flag a player who goes to the ground as part of religious expression, and as a result, there should have been no penalty on the play."

And yet there was. Abdullah's team was given a penalty.

We have no reason to believe that the referee acted out of prejudice or bigotry. It is more likely that he simply did not recognize Abdullah's gesture as a prayer. But even if his decision was the result of ignorance, rather than discriminatory intent, it still matters.

If prayer is an exception to the rule against "going to the ground," then then the NFL's referees need to recognize what prayer looks like in religions other than Christianity. If they can't, then the rule becomes an advantage for Christian players, and a burden on those who practice other religions.

As it happens, the penalty in this case did not have serious repercussions. Kansas City still won the game, 41-14, and the NFL has said that Abdullah will not be fined for his conduct. But the NFL still has work to do. Being a practicing Muslim shouldn't come with a 15-yard penalty.