Adam Sandler's That's My Boy opening: How bad was it?

It was no secret that Adam Sandler’s “That’s My Boy” was a dog: For starters, I called it “Sandler’s latest summertime dog” in my review the other day.

Sandler movies never get good reviews, so this was no surprise. The 23 percent rating it earned on Rotten Tomatoes is pretty much par for the course for Sandler, and was actually better than his last three films. (“Funny People” earned a 68 percent but I don’t count that as an “Adam Sandler movie,” the same way I don’t count “Punch Drunk Love” or “Spanglish” as “Adam Sandler movies.” Those are movies that Adam Sandler is in, but they’re not assembled as Sandler vehicles the same way the majority of his films are.)

While the critical bashing of “That’s My Boy” was anticipated, the audience reaction wasn’t. The film earned just $13.4 million its first weekend, the lowest opening for a Sandler-headlined film since he became a box office star in 1998, when “The Wedding Singer” opened to $18 million on its way to an $80 million gross. (Note: The animated “Eight Crazy Nights” opened to $9.4 million in 2002, but that was a cartoon, and “Reign Over Me,” “Spanglish” and “Punch Drunk Love” all opened smaller, but like I said we’re not counting those as “Adam Sandler movies.”)

So what happened with “That’s My Boy?” The R-rating didn’t do it any favors; Sandler vehicles usually safely preside in PG-13 territory, and the added raunch of “That’s My Boy” — including multiple semen gags and the always hilarious octogenarian sex jokes — limited its audience and hurt its bottom line.

And the pairing with “SNL” star Andy Samberg did nothing for audiences. The pair was co-billed above the title, but Samberg has a long way to go to becoming a movie star.

But there’s another factor at play, which we’ll call “The Jack and Jill Effect.” Last year’s “Jack and Jill” — which starred Sandler in dual roles as a brother and a sister, such a bad idea that it seemed like one of the fake movies his character in “Funny People” would have starred in — was the most maligned Sandler film to date, earning a paltry 3 percent on Rotten Tomatoes, Sandler’s lowest rating ever. (“Grown Ups,” with 10 percent, is second.) “Jack and Jill” was the first Sandler flick to not earn $100 million at the North American box office since 2000′s “Little Nicky,” and its failure signaled a sort of Sandler fatigue, with audiences finally stepping up and saying they weren’t going to support any old slop he throws at them. That apathy seems to have extended to “That’s My Boy.”

So what now? Sandler remains one of the planet’s biggest box office stars, and box office returns don’t seem to bother him all that much. Next up he’s got his first-ever sequel, “Grown Ups 2,” and while all Sandler films rely on a certain amount of comfort and familiarity, this one will offer it outright. And if audiences reject it, he’ll know he’s in trouble.