One team is thriving with a stingy defense.
The other is struggling with an inept offense.
Both face a critical test when they meet Sunday night.
Are the unbeaten Cincinnati Bengals that good?
Are the New England Patriots that bad?
"It's a good chance for us to go out there and put it on tape and show the whole nation this Cincinnati team is real," nose tackle Domata Peko said.
The Bengals haven't won a playoff game since Jan. 6, 1991, when they beat the Houston Oilers 41-14, the same score of last Monday night's Patriots loss at the Kansas City Chiefs.
Now the Bengals (3-0) are the AFC only team without a loss, have allowed an NFL-low 11 points per game and have outscored opponents by an average of nearly 16. And they're listed as a slight favorite in the Patriots' stadium.
"This team is playing with a lot of confidence," Cincinnati quarterback Andy Dalton said. "We've got to keep that going. We're confident in ourselves and we feel like nothing can hold us back."
Certainly not the offensive line of the Patriots (2-2).
The sacks tell the story: none against Dalton, nine against Tom Brady.
Coach Bill Belichick has rotated players assigned to protect his quarterback from game to game, even within games.
Against the Chiefs, rookies Bryan Stork at center and Cameron Fleming at right guard got their first pro starts.
The lack of protection has made Brady appear skittish, getting rid of the ball early, and given his mediocre group of receivers little time to get open. Only three teams gained fewer yards than New England through the first four weeks of the season.
Are the problems correctable?
"I hope they're correctable," Brady said. "I don't think we should feel sorry for ourselves. We've always found a way to kind of grind our way through tough times."
There haven't been many for one of the best quarterbacks in NFL history and a team that has won 10 of the past 11 AFC East titles.
"Guys are going to see this as a chance to fight and get better and pull ourselves out of a situation where most people have turned their backs and said we're not good," Patriots safety Devin McCourty said. "I think we have enough older guys here to understand one loss isn't going to change the outcome of the season."
Or how the Bengals view the Patriots.
"The perception hasn't changed," Dalton said. "The way that game turned out doesn't show the kind of team that they are."
Some things to watch for as the Bengals seek their first 4-0 start since 2005:
PRIME-TIME PROBLEMS: Dalton shrugged off his 2-4 record in prime-time games in his first three NFL seasons. Most of that failure has come on the road where he's 1-3.
"We're not worried about the past," he said. "It's about what we're doing now. So we're excited about getting the opportunity to play Sunday night against a good team and to really show what this team's made of."
SHORT WEEK, LONG WEEK: The Patriots had one less day than usual to prepare after playing Monday night. The Bengals had plenty of time to rest and get ready during their bye week.
"I'm sure coming off the bye week they'll be fresh and ready to go," Belichick said.
Under coach Marvin Lewis, Cincinnati is 6-6 in games before a bye and 4-7 after one.
SOME HELP, PLEASE: Cornerback Brandon Browner and wide receiver Brian Tyms practiced with the Patriots for the first time this season after serving four-game suspensions for violating the NFL's substance abuse policy.
LAST YEAR: The teams also met in the fifth week of the season in 2013 and it was the Patriots (4-0) who were unbeaten at that time. But they lost in Cincinnati 13-6 as Brady's streak of 52 games with a touchdown pass, two less than Drew Brees' NFL record, ended.
"This is a team that gave us all we could handle last year," Brady said, "and it's a great opportunity for us to go out on a Sunday night game and try to play a lot better than we played last week."
PICKOFF PLAYS: The Bengals and Patriots are tied for the AFC lead with six interceptions each. Dalton has thrown just one this season, while Brady threw his only two interceptions Monday night. Belichick reminded his players that the Bengals have "six No. 1 draft picks in the secondary alone," Brady said, "so we've got our work cut out for us."
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