Four teams dominated the NFL over the first half of the season. Each of those teams declined somewhat in the second half, but each one won enough games to get the first weekend of the postseason off. Now each must defeat a challenger that has come on strong over the past few weeks.

SEAHAWKS (11–6) at PACKERS (13–3)
Saturday, 4:30 p.m., FOX

Seattle and Green Bay are two teams that know each other very well and share a number of similarities. Both teams run Bill Walsh-influenced offenses, which depend upon the quarterbacks finding the open receiver when a defensive is blitzing, and the receivers gaining yards after the catch. (Green Bay led the league with 5.8 average yards after catch, while Seattle had a less impressive but still aboveaverage 4.8.) Seahawks head coach Mike Holmgren won a Super Bowl in Green Bay, and quarterback Matt Hasselbeck began his career as Brett Favre’s backup.

There also are some similarities in the running game. Both teams had a terrible time running the ball over the first half of the year. Green Bay improved its running game by handing the starting job to undrafted Ryan Grant, while Seattle finally realized that former MVP Shaun Alexander is a shell of his former self and gave more carries to backup Maurice Morris.

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) say that the Packers’ running game improved from 15th over the first half of the year to fourth in the final eight games. The Seahawks’ running game improved as well, to 12th from 31st.

Both defenses were also stronger against the run than against the pass in 2007, but the similarities finally end when you look at each team’s pass coverage scheme. The Seahawks play primarily in a Cover-2 zone, which will limit the yards after catch that are so important to the Green Bay offense. In front of that zone is an excellent pass rush, which was key to Seattle’s wild card victory over Washington.

Unlike the Seahawks, the Packers’ defense plays primarily man coverage, with an average pass rush from the front four. Opposing quarterbacks completed just 55% of passes against Green Bay, tied for the lowest percentage in the NFL — but when they did complete passes, receivers averaged 5.7 yards after catch, the highest figure in the NFL.

If Seattle upsets Green Bay, penalties will probably play a large role. The Seahawks had fewer penalties than any other team in the league this year. The Packers ranked fourth in penalties and led the league in defensive penalties by a large margin. Green Bay handed the other offense 34 free yards each game because of penalties, more than twice the NFL average.

JAGUARS (12–5) at PATRIOTS (16–0)
Saturday, 8 p.m., CBS

Based on our weighted DVOA formula, which lowers the strength of earlier games to give a more accurate view of how good teams are right now, this game matches up the two best teams in the NFL.

As most fans know, the Patriots haven’t dominated over the past few weeks the way they did in September and October, but they still outplayed 15 of their 16 opponents with only one win the system considers “lucky” (against the Ravens). The Patriots’ offense has been spectacular for the entire season, but the defense has faltered a bit. Through midseason, our DVOA ratings ranked the Patriots fourth in pass defense and 10th in run defense. Since that game, the Patriots rank just 22nd in pass defense and 21st in run defense.

Jacksonville has improved on both sides of the ball since Week 9 — the week they were blown out by New Orleans with backup Quinn Gray at quarterback. During the first eight games of the year, the Jaguars ranked 10th in pass offense and 14th in run offense.

The defense has improved as well. Through Week 9, Jacksonville ranked 13th in pass defense and 27th in run defense. Since Week 10, the Jaguars are fourth in pass defense and 14th in run defense.

And yet, despite all this, New England was still a far better team than Jacksonville over the entire course of the season. Comparing each unit based on rank obscures just how dominant the Patriots’ passing game was in 2007. The difference between the Patriots and the offense ranked second in passing for the year (Indianapolis) was five times larger than the gap between the top two run defenses, seven times larger than the gap between the top two pass defenses, and 15 times larger than the gap between the top two rushing offenses.

Jacksonville is playing very well, but the Patriots just finished the greatest regular season in the history of professional football. That doesn’t guarantee them a title, but it does mean that nobody should expect them to lose until it actually happens. If it does happen, the team to beat them will probably be archrival Indianapolis, not Jacksonville.

CHARGERS (12–5) at COLTS (13–3)
Sunday, 1 p.m., CBS

Of course, that rematch won’t happen unless Indianapolis gets past San Diego first. The Chargers have already beaten the Colts, although it was one of the strangest games of the year.

San Diego beat Indianapolis 23–21 at home in Week 10 thanks to special teams and an injury-decimated Colts offense. The Colts played that game without their starting left tackle and three of their four top receivers. Stuck throwing with Reggie Wayne and a bunch of inexperienced practice-squad types, Peyton Manning had a career-high six interceptions. The Colts’ special teams allowed San Diego’s Darren Sproles to return both a kickoff and a punt for a touchdown. Despite all this, the Colts nearly pulled out a win with a last-second drive — until Adam Vinatieri, Mr. Clutch, missed an easy 29-yard field goal.

This time, the injury problems belong to San Diego, not Indianapolis. Left tackle Tony Ugoh, wide receiver Anthony Gonzalez, and tight end Dallas Clark are all healthy for the Colts after missing the first game. The Colts say that even future Hall of Famer Marvin Harrison is healthy again after missing 11 games this year.

Meanwhile, the Chargers will probably be without their great tight end, Antonio Gates, due to a toe injury he suffered during last week’s win over Tennessee. Without Gates, quarterback Philip Rivers loses his security blanket on third down. The Chargers threw to tight ends 38% of the time on third down — more than twice the league average of 17%.

On first and second down, the Gates injury will affect the Chargers’ running game more than their passing game. The Colts were the second-best team in the league at stopping tight ends, thanks in large part to Defensive Player of the Year Bob Sanders. With Gates in the lineup, the Colts will need to use Sanders more in pass coverage. Without Gates, the Colts are free to make Sanders the eighth man in the box on anything that isn’t an obvious passing situation. That makes life hard for last year’s MVP, running back LaDainian Tomlinson.

One thing this week will be the same as it was in the the first game: San Diego’s dominance on special teams. The Chargers rank fourth in Football Outsiders’ special teams ratings, above average in every respect. Indianapolis ranks last, well below average in everything except punt returns. Vinatieri may be the highest-paid kicker in the league and a possible Hall of Famer, but this year the Colts ranked 29th in net kickoff value and 31st in field-goal kicking.

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