The NFL is built on rivalries, sometimes between teams, sometimes between players. This weekend you’ll find two high-powered offenses fighting for first place in their division, and two burgeoning stars fighting for the title “most promising third-year quarterback.”

SEAHAWKS (2-2) AT RAMS (2-2)
(Sunday, 1 p.m.)

These two NFC West division rivals met three times last year: twice in the regular season, and once in the playoffs. Each time, statistics said that Seattle was the better team going in. Each time, St. Louis was the victor on the field. This year, once again, statistics say Seattle is the better team going in. Can the Seahawks finally defeat their nemeses?

The Seahawks played well enough to beat Washington last week, but Josh Brown’s field goal with time expiring clanked off the uprights. In overtime, Seattle astonishingly allowed Washington to convert twice on third-and-10 and once on third-and-nine. In fact, Washington had third down with nine or more yards to go nine times during the game, and converted eight times.

The strangest part of this defensive meltdown is that the Seahawks’ defense had been outstanding on third downs through the first three weeks of the season. In those games, Seattle opponents were just 9-for-37 converting third downs. Last week, the Redskins, who average 14 points a game, were 13-for-18.

Seattle’s offense, at least, is clicking on all cylinders, ranking third in the league with 4.8 yards per carry and fourth in the league with 6.1 yards per pass. A showdown with the Rams, who are allowing almost 28 points a game, should only accentuate those impressive numbers.

The Rams have become the football equivalent of ‘mac and cheese’: not very good, but at least you know what to expect. As usual, the Rams have a good passing game, poor special teams, and a terrible defense. (You may read that the Rams are a top 10 defense against the run, but this is based on yards per game; they are actually 20th in yards allowed per carry, but why run on the Rams when their pass defense is even worse?) The difference this year is that the running attack is much weaker due to the injury to new starter Steven Jackson, who bruised his sternum midway through a narrow Week 3 win over Tennessee. Before the injury, Jackson was averaging 4.2 yards per carry; since returning to the field in the fourth quarter of the Tennessee game, that average has plummeted to just 2.2 yards per carry.

Since the playoffs expanded to 12 teams in 1990, there have been eight instances when one team lost to a division rival three times in the same season. The Seahawks are one. The other seven teams, after going a combined 0-24, went 6-8 against the same division rivals the following year. There is no reason to believe the Rams have some sort of mystic hold on the Seahawks that keeps Seattle from winning.

But when Seattle finally does beat the Rams, it’s not likely to happen in St. Louis. Seattle’s problems on the road are a bit overstated: Since joining the NFC West in 2002,the Seahawks are 10-16 on the road in the regular season. That’s a .385 winning percentage, and the NFL average for road teams is .410. But the Rams’ dominance at home is not overstated. Since 2002, the Rams are 21-4 at home during the regular season and just 8-19 on the road.

If Jackson is still slowed by injury, the Rams will be stuck in a lot of thirdand-long situations. On the road, against the Seattle defense of the first three weeks, that would be a problem. At home, against the Seattle defense from last week, it won’t keep the Rams from a win.

BENGALS (4-0) AT JAGUARS (2-2)
(Sunday, 8:30 p.m.)

Carson Palmer and Byron Leftwich will forever be linked as the top two quarterbacks to be taken in the 2003 NFL Draft. Now they provide a good example of why an offense needs more than just a quarterback to build on. Palmer, surrounded by other talented players, leads the surprising 4-0 Bengals. Leftwich, with one good receiver and a running game averaging under 100 yards a game, leads an ineffective offense that wouldn’t even be 2-2 without strong play from a stalwart defensive unit.

But is the Jacksonville defense as strong as we all thought? Last year, according to Football Outsiders’ Defense adjusted Value Over Average ratings (DVOA) – which break down each play of the season and compare it to the NFL average based on situation and opponent — Jacksonville’s defense ranked eighth against the pass and 11th against the run; This year, those numbers are third and 30th, owing in large part to problems on second and third downs.

So how do you run against a Jaguars defense whose strength comes up the middle, with defensive tackles John Henderson and Marcus Stroud backed by linebacker Mike Peterson? You run around them. Only 43% of runs against Jacksonville this season are listed as going behind the center or guards, the third-lowest total in the league. Cincinnati has even more reason to work running backs Rudi Johnson and Chris Perry to the sides after both starting center Rich Braham and backup Larry Moore were injured last week in a close win over Houston. (Braham will attempt to play despite a sprained MCL.)

Star receiver Chad Johnson will always be the focus of the passing game, but watch out for underrated Cincinnati tight end Matt Schobel. Both the Broncos and the Jets had success throwing to their tight ends against Jacksonville, and Schobel, at 6-foot-5, 255 pounds, is one of the game’s biggest secrets when it comes to moving the chains on third down.

Many people feel the Bengals defense will wilt when finally tested by a strong offensive team, but Jacksonville is definitely not that team. The rapid aging of Fred Taylor continues, with the veteran back averaging just 3.3 yards per carry this season, and the Jacksonville passing game is still Jimmy Smith and the seven dwarfs.

At least Leftwich is good at avoiding what has been the hallmark of the Bengals defense this year: interceptions. Cincinnati leads the league with 12, but Leftwich has thrown just three.

Mr. Schatz is the editor in chief of FootballOutsiders.com.