Here's a look at one area of concern, one crucial question, confronting the league's three remaining undefeated teams:
Carolina: Is the passing game good enough to win a game in which the opposition defense shuts down tailback Stephen Davis?
So far, quarterback Jake Delhomme has done a superb job managing games, but there will be a time when the first-year starter has to actually win a game with his arm. The Panthers statistically rank 31st in the league in passing offense, not surprisingly second in rushing offense, but some opponent is going to commit eight in the box and, in so doing, force Delhomme to make big plays. He has done so, but on rare occasion, and is far more comfortable being a complementary player rather than The Man. Losing wide receiver Kevin Dyson to a knee injury in the spring really hurt the vertical dimension. Steve Smith can get deep on occasion but, at his diminutive size, might wear down as the season grinds on. Muhsin Muhammad has evolved into a possession receiver and has just one catch of more than 20 yards.
Kansas City: When will the offensive explosiveness demonstrated in 2002, when the Chiefs led the NFL in scoring with 467 points, return for the Chiefs?
Prior to last week's incredible comeback at Green Bay, when Kansas City trailed by 17 points in the fourth quarter, the Chiefs had been getting virtually all their big plays from two performers: tailback Priest Holmes and kick return ace Dante Hall. But the win at Green Bay might have signaled the return of the outside passing game, as Trent Green threw for 400 yards and got his three key receivers -- wideouts Johnnie Morton and Eddie Kennison and tight end Tony Gonzalez -- a lot more involved. Green has not turned the ball over much but, until last week, hadn't thrown many touchdown passes either. Even with Holmes, arguably the league's premier all-around back now, as the centerpiece, the offense has to show diversity. For the first month of the season, the Kansas City passing game pretty much went sideways. At some point, the Chiefs need more stretch.
Minnesota: Can the improved defense, which has demonstrated an opportunistic bent under coordinator George O'Leary, continue its excellent play?
The Vikings aren't the most physically imposing team upfront. Even standout tackle Chris Hovan is hardly a space-eater, and the unit relies on quickness and scheme much of the time. Through the first five games, the Vikings have been able to run around enemy offenses and the advantage in quickness has forced turnovers. Safeties Corey Chavous and Brian Russell, for instance, have nine interceptions between them. But it might be interesting to see how the Vikings, who typically play with a lead, react if they're behind in a game against a physical opponent that has the luxury of pounding the ball. The Vikings have plundered virtually every opponent to date and, given their coverage schemes, are likely to continue the larcenous streak. But this is a unit that is not very big that will be tested by some power running games before long.
Len Pasquarelli is a senior NFL writer for ESPN.com.