Orlando Scandrick, one of the best players on an abject defense, will miss the first four games of the season after violating the NFL’s substance-abuse policy.

And you thought a defense that allowed 415.3 yards and 27.0 points per game last season couldn’t get worse.

Well, it just did. This is a huge hit for a team with a shaky cornerback situation.

Morris Claiborne hasn’t practiced in more than a week. He has yet another training camp injury that prevented him from playing in the preseason opener for the third consecutive season.

Brandon Carr missed the first three weeks of training camp to be with his family as he dealt with the death of his mother.

Neither one of those guys plays with the edge Scandrick does, which is important on a unit devoid of playmakers. He’s the one cornerback not afraid to challenge Dez Bryant on every snap of each practice.

He always believes he’s the best player on the field -- even when it’s clear that he’s not. Scandrick’s unshakable confidence has helped make him a good player.

Understand, Scandrick is also one of the smartest players on defense, which is why it’s hard to believe he did something so dumb. He reportedly took a drug that’s on the NFL’s banned list while vacationing in Mexico.

There’s no acceptable excuse for that.

All players have to do is check with the NFL to see whether whatever they’re about to ingest is on the list. If they don’t, they deserve whatever happens.

In this case, it’s a four-game suspension that will force him to miss games against San Francisco, Tennessee, St. Louis and New Orleans.

A bad defense just became worse. And one of its best players is to blame.