The NFL's 80th season opens today with dramatic changes all around. Arguably the most significant will be the return of instant replay for the first time since 1991 to help officiating crews avoid the blunders of previous years.

The new challenge system won't always work because some controversial calls and a number of judgment penalties--pass interference and holding, among others--will not be subject to review. Still, there clearly is a consensus among coaches, who have two challenges per game, and league administrators that some replay system is better than none.

"I don't anticipate any problems," said Chris Palmer, the rookie head coach of the expansion Browns, who begin play tonight in Cleveland against Pittsburgh. "The only flaw that I see, and you can't correct it, we had a play [in preseason] where there was a pass caught and we thought it was fumbled. But the officials had already blown the whistle, so it's got to go back to the other team, and there's no way to correct that no matter what happens. Other than that, I thought replay was excellent."

Palmer is one of six head coaches making his debut, joining Brian Billick in Baltimore, Dick Jauron in Chicago, Gunther Cunningham in Kansas City, Mike Riley in San Diego and Andy Reid in Philadelphia.

"I've got butterflies already," Palmer said on Wednesday. "It's hard to keep the food down."

Several veteran head coaches have switched sidelines, the most prominent being Mike Holmgren leaving Green Bay for Seattle, where he's also general manager. He was replaced in Wisconsin by Ray Rhodes. And George Seifert comes out of retirement to join the Carolina Panthers.

Thanks to free agency and a $57 million salary cap, there are lots of players wearing different uniforms, including $21 million wide receiver Raghib Ismail moving from Carolina to Dallas.

The rookie class of '99, with five quarterbacks taken in the first round, also is expected to have a major impact. Rookies attending a symposium earlier this year were asked which player had the best chance to be rookie of the year. The overwhelming choice: New Orleans running back Ricky Williams, who injured an ankle in the preseason but will start at home today against Carolina.

None of the five first-round quarterbacks are expected to start today, though Jauron said he plans to alternate veteran Shane Matthews with rookie Cade McNown in Chicago's opener against Kansas City at Soldier Field.

Veteran journeyman Ty Detmer will start for the Browns, but first overall pick Tim Couch has been a quick study and could see action if the offense struggles as it did in the preseason.

In Denver, retired John Elway likely will be in the owner's box Monday night when the Broncos play host to Miami. Elway rode off into the sunset as the Super Bowl MVP after Denver won its second straight title. So Dan Marino, drafted the same year as Elway (1983), will be the oldest quarterback on the field.

Second-year player Brian Griese beat out Bubby Brister for Elway's former job in a controversial training camp decision by Coach Mike Shanahan. As long as Terrell Davis, who rushed for 2,000 yards in '98, stays healthy, the Broncos should contend for what would be an unprecedented Super Bowl three-peat.

In the NFC, the Minnesota Vikings generally are considered the team to beat, even if Billick, their offensive mastermind, is now drawing up plays in Baltimore. The Vikings also lost several key players to free agency--cornerback Corey Fuller, run-stopping defensive tackle Jerry Ball and defensive end Derrick Alexander, all now in Cleveland. But wide receiver Randy Moss is still in the lineup, and apparently better than ever after a remarkable rookie season with 17 touchdown catches.

"We've changed Randy's arsenal this year," said quarterback Randall Cunningham, who also had a career year in '98. "We're still working on the short stuff, but he has an arsenal of new stuff he'll use this year. Teams are going to double cover him, but when they don't, we're going to take advantage of it. We have some stuff in place that will be fun to watch."

They'll put it on display today in Atlanta in a rematch of last season's NFC championship game won by the underdog Falcons in overtime in Minneapolis.

"I don't think there could be anything better than playing the first game in Atlanta and then playing the last game in Atlanta," said Vikings Coach Dennis Green.

"Nothing's changed," said Atlanta running back Jamal Anderson. "They have the same personnel, the same situation. Let's be frank. A lot of people thought it was a fluke (last year) or that things that happened were just improbable and couldn't happen again. We're used to being underdogs. We're used to being a team people don't have high expectations for. That's fine with us."

In the AFC, Jacksonville, Miami and the New York Jets all are poised to make a serious run at overtaking the Broncos. But don't count the defending champions out just quite yet.

"People are focusing to see what are the Broncos going to be without John Elway," said linebacker Bill Romanowski. "I think they're going to be surprised. A lot of people are saying, 'Well, they're not going to be as good without John.' They've got another thing coming, because we're going to be a great football team."

Like many things in the NFL this year, that too will be subject to further review.