Last season, seven NFL teams started 3-0 and only one made the playoffs – Oakland, which had to suffer through a four-game losing streak before turning back around and getting to the Super Bowl.

So there are no guarantees for anyone yet this season.

Still, most of the unbeaten teams after four weeks seem legitimate, especially Minnesota, which established itself by thrashing San Francisco on Sunday after beating the other three teams in the dismal NFC North.

OK, the 49ers seem to be in trouble, but that’s another issue (like why Steve Mariucci was fired).

“We know how good we are,” said tackle Chris Hovan, the Vikings’ defensive leader. “We just don’t talk about it like other teams do. We’re not going to go out and yap. We have to prove it on the field.”

After Sunday’s games, Minnesota and Indianapolis are 4-0. So are Denver and Kansas City, who meet next week at Arrowhead Stadium. Carolina and Seattle are both 3-0.

A look at the unbeatens (in no particular order):

• Minnesota: Sunday’s win, the seventh in a row over two seasons, was more impressive than the first three. The defense, the Vikings’ weak point even when they were strong, held San Francisco to 125 yards in the first half Sunday when the game was still in doubt. Rookie defensive tackle Kevin Williams, who has combined with Hovan in the middle of the line, had two sacks.

Gus Frerotte was better than a solid replacement for Daunte Culpepper – 16-of-21 for 267 yards and three TDs. He’s not a starter anymore, but he’s a perfect backup.

• Indianapolis: Forget all the heat Peyton Manning has taken the last couple of seasons for interceptions and multiple checkoffs, six TD passes (without Edgerrin James in the lineup) demonstrates he’s still 1-2-3 among NFL QBs. Even more important, the no-name defense (OK, Dwight Freeney is a name) is better in Tony Dungy’s second season than in his first.

Still, the Colts have just one win that counts – Tennessee at home. The victory in New Orleans came against a team that started with a questionable defense, then lost five starters to injury.

• Denver: Jake Plummer isn’t the next John Elway, but he’s been fine since a dreadful opener. The Broncos survived the dreaded “sandwich game” by struggling past Detroit between a win over Oakland and a huge game in Kansas City next Sunday.

• Kansas City: Dick Vermeil has always won big in his third season with a team, Priest Holmes got healthy and the defense has improved. It’s not only free agents Shawn Barber and Vonnie Holliday, it’s DT Ryan Sims. In his second season, Sims has become an inside force.

And, of course, there’s Dante Hall, who has six returns for touchdowns in his last nine games. After four games (three TD returns), you almost could argue his case for MVP, even on a team that has Trent Green, Priest Holmes and Tony Gonzalez.

• Carolina: Sunday’s game was perfect – Stephen Davis ran for 158 yards and the defense held the Falcons to a field goal. The players also recognize they’ve done nothing yet – they were 3-0 last season,

lost eight straight and finished 7-9.

“So we’re celebrating now, but not for long,” said safety Deon Grant, who had a

career-high 12 tackles against Atlanta.

• Seattle: Probably better than the Rams and 49ers, who they lead in the NFC West. Ray Rhodes, the new defensive coordinator, has put together a more aggressive defense that won’t get back the injured Shawn Springs for a month.

It also helps that Mike Holmgren is a full-time coach now. The Seahawks have six wins, including the last three of last season.

Other observations

A lot of Philadelphia fans wrote off the Eagles (1-2) when they scored just 10 points in their opening two losses. They got 23 in Buffalo on Sunday when Donovan McNabb rushed for 47 yards. When McNabb gets out of the pocket, the Philadelphia offense is much better. … The NFC East could be a four-team race. The Redskins (3-1) and Giants (2-1) will be around all season. Dallas (2-1) is a question mark, but Quincy Carter is starting to make Jerry Jones look smart for taking him in the second round of the 2001 draft when most people thought he was at best a fifth-rounder who could play “slash.”

The AFC North is so bunched that Cincinnati (1-3) is only a game out of first place after winning its first game under Marvin Lewis in Cleveland on Sunday. Pittsburgh (2-2) is probably the default winner although Baltimore (2-2) won a Super Bowl with just Jamal Lewis on offense and a great defense. The difference is that the quarterback then was a veteran, Trent Dilfer, rather than raw rookie Kyle Boller.

Tennessee (3-1) is what it has been for the past four to five seasons – Steve McNair and a bunch of guys with no national reputations. One guy who is known, Eddie George, is averaging 2.8 yards a carry, but the Titans will be there when the playoffs start.

Despite its comeback win Sunday, Oakland (2-2) doesn’t look like a Super Bowl team in a division that includes the Broncos and Chiefs. The Raiders’ wins are over the Bengals and Chargers, a combined 1-7, and they could easily have lost to both.

Conventional wisdom says the Jets (0-4) are winless because they lost Chad Pennington. But the loss of Laveranues Coles hurts New York as much as it has helped the Redskins and the Jets also miss G Randy Thomas, another defector to Washington.

And …

Was Buffalo a mirage?