Zach Thomas needs to play well for Miami to stall Terrell Davis.

As the two-time defending champions, the Denver Broncos are the team to beat. But when I look at the Miami Dolphins, I see the best defense in the AFC. They have an outstanding group on the defensive line, at linebacker and in the secondary.

Miami's pass defense was the best in football last year. The Dolphins allowed a completion rate of only 50 percent, giving up 17 touchdowns and intercepting 29 passes. Sam Madison and Terrell Buckley are in-your-face cornerbacks. They will be physical, nasty and tough, an approach perfectly suited for defensive coordinator George Hill's aggressive style.

The Dolphins defense could spell trouble for Brian Griese, who's getting his first start as the Broncos enter the post-John Elway era. But the Broncos will surround Griese with one of the league's most talented rosters, led by league MVP Terrell Davis.

Here are the keys to success for each team:

Miami Dolphins
1. Zach Thomas must maintain control: When I looked at the film of last year's AFC divisional playoff game, which Denver won 38-3, Thomas played out of control. He is one of the game's best middle linebackers, but it's important that a player maintains the discipline of the defense.

INSIDE THE NUMBERS

Better and better: Dolphins receiver O.J. McDuffie finished last season with a career-high 90 receptions. Entering his seventh year, McDuffie has improved his reception numbers every season. Still, 90 will be tough to top in '99. Champs turn chumps: This is the 13th time the defending Super Bowl champions have opened the season on Monday Night Football. The champs have only gone .500 in those games, going 6-6. TDs for TD: Terrell Davis has scored a touchdown in all four season openers during his career. However, Davis' average yards per carry in openers (3.6) is more than a yard less than his career average (4.8).

Too often, Thomas was too eager to make plays and be aggressive. He lost his gap responsibility and allowed Davis the cutback lanes he's so good at finding. He has to play under control, maintain his gap responsibility and not allow those big cutback lanes.

2. Establish a running game: The Dolphins have talked about their running attack for years. Last year, they started moving a little bit in the right direction. They ranked third in the league in time of possession and controlled the football well. But the Dolphins are still looking for the back they will feature.

Right now, it's still running back by committee, with Karim Abdul-Jabbar, rookie Cecil Collins and others. Jimmy Johnson hasn't really settled on the player who will be his go-to back. I think eventually someone will emerge and carry 20-25 times a game. Because Collins' health is still in doubt, Jabbar will start and play until everyone is healthy, and then you'll see the competition open up again.

3. The effectiveness of Tony Martin: Controlling the football is all well and good because it keeps your defense on the sideline. But the Dolphins have to produce points. With Martin added to the offense, they now have the ability to score.

To measure the impact Martin had on the Falcons offense last year, Chris Chandler had the No. 1 average in yards per pass attempt, and that's a different product of the big-play ability of Martin.

In talking to secondary coaches and players around the league, the one thing everyone fears is speed. And Martin brings speed to the Dolphins offense. That's the one thing Dan Marino hasn't had for a number of years, a receiver who can stretch the defense vertically.

Denver Broncos
1. Brian Griese: When you start an inexperienced quarterback, what is his play going to be like? I don't care what anyone says -- Griese, Bubby Brister or Chris Miller. With John Elway gone, the Broncos will have a tremendous falloff at quarterback. I'm referring not only to ability, but also to leadership and command of the offense.

PLAYERS TO WATCH

Richmond Webb, Dolphins LT: Although he held out all preseason and didn't sign until just last week, Webb will be at his usual spot, protecting Dan Marino's blind side. Yatil Green, Dolphins WR: In 1997, Green's season ended in July. In 1998, it ended in August. This year, Jimmy Johnson is ecstatic that Green has finally made it to September. Can he contribute? Sam Madison, Dolphins CB: With Dale Carter now in Denver, the up-and-coming Madison might be the best corner the Broncos face this season. Matt Lepsis, Broncos RT: The most celebrated change in Denver's lineup is at quarterback, but Lepsis is another Bronco making his first start. Al Wilson, Broncos LB: The Broncos are very high on the rookie linebacker, and they think he might be the next John Mobley. Howard Griffith, Broncos FB: Perhaps the best blocking fullback in the NFL, Griffith is the man who helps Davis get loose.

The Broncos will have a much more limited approach offensively. Mike Shanahan, who is probably the best designer of plays in football, has always been able to put the Broncos in a situation where they could score early through formation variation and dictating matchups. He has a unique ability to create a matchup and generate big plays.

With Griese, it will be tougher to get those matchups because Griese won't be as proficient at reading the coverage and knowing where to go with the ball if he is facing a unique coverage. How will Griese respond?

He is playing against probably the best pressure defense in football. One thing the Miami cornerbacks do well is read the quarterback's eyes. No matter how well Griese is coached, it will be a lot different when he's in the game. The speed of the game is so much quicker, he has to be very careful not to lock onto a receiver because he will throw interceptions if he does.

2. Dale Carter's impact: I thought last year Ray Crockett played well at one corner for Denver. Carter, as an aggressive, bump-and-run style of defender, is one of the better cornerbacks in NFL history.

Carter didn't have a good preseason. On tape, it looked like he was struggling. But if Carter and Crockett play well on the corners, it will free up defensive coordinator Greg Robinson to immediately attack the line of scrimmage with his blitzing schemes. Robinson does a great job of designing schemes to get players in Marino's face, so I look for Denver to play an aggressive style of defense.

Steve Atwater is no longer in Denver's secondary, and Eric Brown replaces him at safety. Denver will miss Atwater's experience. Brown has had some playing time, but he's not Atwater. Because of that, Robinson might be limited in the packages they may want to use, but Carter's effectiveness on the corner can make everyone better.

3. Offensive line play: In Miami's regular-season victory over Denver last season, the Dolphins established the line of scrimmage defensively. Tim Bowens played in that game, but not the playoff game. His absence was a big loss for the Dolphins.

The Broncos have maybe the best offensive line in football in terms of team blocking. They stick and stay on their blocks and then cut-block, putting defenders on the ground. If they can get the Miami defensive linemen on the ground, the Broncos will move the ball. If the Dolphins can stay upright and clog the cutback lanes with their front four, they can slow down the running game.

The only change on the Broncos offensive line this year is Matt Lepsis at right tackle in place of Harry Swayne, who signed with the Ravens. Lepsis is a solid player, so there won't be any huge loss with him filling in. Alex Gibbs could be the best offensive line coach in the NFL. He knows how to get the five linemen plus tight end Shannon Sharpe to all block as one.