The Cincinnati Bengals were more than good Sunday, but they didn’t ruin Robert Griffin III’s home debut for the Washington Redskins. No. This was an inside job, perpetrated by the very people who were supposed to have their rookie quarterback’s back, committed by the one unit Mike Shanahan “thought was going to be the strength of our football team.”

It’s 4 p.m. Sunday, Washington. Do you know where your defense is?

Getting scored on. Again.

“You can’t go out and ask a rookie quarterback to put up 40 points every week,” Lorenzo Alexander said early Sunday evening after his teammates had cleared out of the locker room. “Thirty-plus points the last three games — we’re not going to win too many games that way. We got to do something.”

London Fletcher described the Redskins’ lousy performance against Cincinnati as “extremely frustrating.

“Defensively we thought we’d be a better unit, and I know we will be,” the defensive captain said.

For the first time since 2005, the Redskins have scored 99 points in three consecutive games combined. But when you give up 101, that still leaves you with a losing record.

A week after surrendering 452 yards to the Rams, the Redskins gave up 478 yards to the Bengals. This sun-spackled day in Landover seemed destined to end with a stirring Griffin-led second-half comeback — that is, until Jim Haslett’s guys couldn’t stop Andy Dalton, A.J. Green or, really, anybody else when it mattered.

The Bengals had six plays of 25 yards or more: three long touchdowns, including a 73-yarder to Green on the first play from scrimmage that dampened the festive spirit before the game was a minute old. That the touchdown came on a trick play — on a pass from reserve wideout Mohammed Sanu — just seemed to rub salt in the wound.

If anyone thought this was an anomaly, it would be one thing. But we’re going on two years now of opponents exploiting a Cover-Zero scheme that lives up to its name: DeAngelo Hall and friends really don’t end up covering anybody.

For the eighth straight game dating from last season, Washington gave up more than 31 points and more than 350 yards. That’s got to really irk the loyalists who waited so long and patiently for an offense to emerge: Now that it has, the holes that need to be patched are on the other side of the ball.

“We felt like we knew what they doing going into it by the way they were playing,” Dalton said after throwing for 328 yards and three touchdowns. “For us, it was just about taking advantage of it.”

I asked Orson Charles, the third-string tight end on the Bengals, what he saw. “On a couple of the big plays, when the Redskins were playing us in a double tight-end set, we saw a lot of man-to-man coverage and Cover-1 that we just exploited.”

Added Green, who shrugged his shoulders when asked if any of the Redskins’ defensive backs gave him problems, “I guess they confident in their corners.”

After watching Josh Wilson embarrassed along the sideline by Bengals receiver Armon Binns for a 48-yard touchdown, you wonder where that confidence comes from.