On the day the NFL lockout ended, if you had declared that after nearly three weeks of the regular season, there would be three undefeated teams, and those teams would be Green Bay, Buffalo and Detroit, you would have been committed. Or mocked — a lot.

Although the Packers may be the best team in the league, the Lions were expected to be good, not great, and the Bills . . . well, the Bills were expected to be improved. They’re improved, all right. They’re leading the AFC East.

Just as surprising, though, is the list of winless teams: Miami. Indianapolis. Kansas City (ouch). Minnesota. St. Louis.

Two of those teams — the Colts and Chiefs — were in the playoffs a year ago. A lot of people, myself included, thought the Rams might make the postseason this year.

The Colts are without Peyton Manning, which is a big loss, but did team doctors decide to rebuild him using parts from the rest of the offense? The Chiefs have had a plethora of bad injuries, but again, teams have injuries all the time. It’s how you deal with them. And St. Louis can still make the playoffs, especially in the weird NFC West.

Meantime, in New York, Roger Goodell and Co. are smiling. The lockout had no discernible effect on the NFL’s greatest strength: parity. (What, you thought it was breathtaking individual performances? Deeply moving films? Fantasy leagues?)

“Any Given Sunday” isn’t just the title of a mediocre movie. It’s actually true. How else to explain how Tony Romo has already gone from goat to hero, and Tom Brady from hero to goat, and we haven’t hit October yet?

The NFL standings are just full of surprises. For instance, the Eagles are 1-2. Sure, they’ve had some bad luck, with Michael Vick suffering a concussion last week and a broken hand this week. But Philly’s offseason moves were supposed to be the NFL equivalent of the NBA’s Miami Heat. (Then again, remember how the Heat’s season started? Maybe this is playing out true to form.)

Could Rex Grossman be — wait for it — correct? Could the Redskins have a shot at the NFC East? The mind boggles — but there are crazier ideas. The Browns have as many wins as the Ravens and the Steelers. Cincinnati has as many wins as the Bears. Cam Newton is third in the league in passing yards (although the Panthers are only 1-2). It’s a world gone mad.

Except, of course, that it isn’t. A fan wants his game to be a guaranteed “W” every week — but wants every other game to be a mystery. Otherwise, why watch? No one but Gators and Wildcats fans would tune in to see Florida beat Kentucky for the 25th straight time Saturday (and I’m not sure about the Wildcats fans; after all, the combined score over that period is 1062-435).

This is what makes the NFL the favorite sport of Americans these days. Anything can happen. My team of record is winless, and I can’t look away. Can you?