GREEN BAY, Wis. — M.D. Jennings was only 16 years old, but the Green Bay Packers safety still can picture Randy Moss that January night in 2005.

“I can remember him wiping his butt on the goal post. I can remember that,” Jennings said. “I was excited to see that happen. When you see someone do things like that, it’s crazy.”

And, no, Jennings would not be thrilled if Moss pulled that stunt Sunday, Sept. 9.

“That’s like a slap in the face if someone comes in your house and does something like that,” Jennings said. “So we have to keep him out of our end zone and not give him a chance at any celebrations.”

So that’s the variable this Sunday in the Week 1 showdown at Lambeau Field against the San Francisco 49ers.

If any team knows the damage a full-throttle, all-in Moss can inflict, it’s the Packers.

In 14 career games against Green Bay, Moss has 1,273 receiving yards and 13 touchdowns. He has tortured the Packers unlike any other. Then again, 13 of those 14 games came at least eight years ago.

He’s 35 years old. He was out of the league last season.

Should any residual fear from those spankings a decade ago remain? The 2012 Moss is a mystery.

“That’s what makes the game that much fun,” Packers cornerback Tramon Williams said. “People want to come in and see the old Randy Moss. They want to see the guy who goes up the field and makes great catches over guys, and that’s the mystery of it.

“You don’t know what you’re going to get. You don’t know if you’re going to get that or if you’re going to get a different Randy.”

Maybe this mystery would be a little clearer if we heard from Moss. Since training camp began, Moss has held only two news conferences and declined multiple interview requests, according to the San Mercury News.

He is one of the greatest enigmas in NFL history — a supremely talented, supremely beat-to-my-own-drum superstar. The man said he plays “when I want to play,” and backed it up.

San Francisco had to juggle all of this when signing Moss off the street to a one-year, $2.5 million contract.

Whether the rest of the league should be scared is unknown. Moss was a complete nonfactor the last time he played in 2010. He caught 28 passes with three teams.

The 49ers are banking that was due more to disinterest than eroding talent. This preseason, Moss had three receptions for 24 yards.

For what it’s worth, the Packers are trying to rekindle Moss memories of 1998, of 2004, of 2007, as much as possible this week.

“I can remember Moss just running through coverage, just throwing his hand up,” Jennings said. “Two or three guys on him. (Daunte) Culpepper would just throw it up to him; he’d run under it and make plays.”

Williams says he is expecting the “old Randy.”

“I think that’s what everybody in the secondary is going to be expecting — the Randy who’s done it at such a high level so many years,” Williams said.

“You can’t look past that. Once a guy puts that on film year in and year out in the league, you can’t look past that.”

There’s reason to buy into Moss. If he was washed up, he would have been cut.

Terrell Owens lasted 20 days in Seattle. Chad Ochocinco … Johnson … whatever lasted one exhibition game. Plaxico Burress remains out of work. Patience runs low for diva receivers of any type.

The fact that Moss is here, apparently ready to make a difference, speaks volumes. He’s doing something all of the above are not — suiting up for Week 1. And on the depth chart released Tuesday, Moss is starting.

“I can’t say how much game he has left,” Jennings said. “He was able to make the 53-man roster, so he really proved something to the coaches on that staff.”

The numbers weren’t there. But after watching the tape, Jennings, like Williams, is bracing for the Moss of yesteryear.

Culpepper and Randall Cunningham aren’t quite heaving prayers to Moss in double coverage anymore. And don’t expect the Alex Smith-led 49ers to lose their identity.

Still, Moss has provided a few nightmares on this field before. On Sunday, the real Randy Moss will stand up.

“We’re not sure where he’s going to be,” Williams said. “But whatever they come with, we’ll be prepared for.”