The NFC champion Seattle Seahawks have the league’s most balanced offensive attack, with MVP Shaun Alexander just one of the five Seahawks selected as offensive starters for the Pro Bowl. The AFC champion Pittsburgh Steelers have demolished three top offenses in three straight games with a swarming, tenacious defense. Which of these standout units can overcome the other to win Super Bowl XL?

Actually, the answer is probably neither. Seattle’s offense and Pittsburgh’s defense will probably play to a draw, leaving the winner of Super Bowl XL to be determined by which early-season weakness can continue its superior postseason performance: Pittsburgh’s passing game, or Seattle’s secondary.

WHEN SEATTLE HAS THE BALL

Seattle’s offense literally has no weaknesses. Only Indianapolis was better in 2005 according to Football Outsiders’ DVOA (Defense-adjusted Value Over Average) system, which breaks down each play of the season and compares it to the NFL average based on situation and opponent.

The running game features the league MVP Shaun Alexander running behind the Pro-Bowl fullback Mack Strong. The offensive line features left tackle Walter Jones and left guard Steve Hutchinson, both the best in the league at their positions, alongside three other above-average linemen.

No NFC quarterback had a better season than Matt Hasselbeck, and his receiving corps is deep and talented –and even better now that top wideout Darrell Jackson is healthy after losing 10 games to injuries. Tight end Jerramy Stevens finally fulfilled his first-round potential with 554 yards and five touchdowns on the season, and the Seahawks can bring in Ryan Hannam when they need a dependable blocking tight end.

Of course, Pittsburgh’s defense can match Seattle’s offense. Pittsburgh’s 3-4 alignment is all about confusion. Every Pittsburgh linebacker is skilled at both rushing the passer and covering receivers, and the opposition never knows if safety Troy Polamalu or even a cornerback is going to be coming while three linebackers drop back into coverage.

The best way to parry an attack from an unknown direction is to block as many paths to the quarterback as possible. The Seahawks have excellent blockers who can stay in the backfield to protect Hasselbeck, including Strong, Hannam, and even Alexander, who made some nice blitz pickups in Seattle’s first two playoff games.

Pittsburgh’s biggest weakness on defense is that those pass-rushing outside linebackers leave a lot of open space for dump off passes to running backs in the flat. The Steelers ranked 30th in DVOA against passes to running backs, and while Seattle doesn’t pass to its backs much, Strong has made some big plays as a receiver.

Those pass-rushing outside linebackers also create running opportunities; the best way to counter a fast linebacker like Pittsburgh’s Joey Porter is often to run straight at him. The Seahawks ran 36% of their running plays to the left, more than any other team in the league – and Pittsburgh allowed 4.7 yards per carry on runs left end, compared to 3.3 yards per carry everywhere else. In the running game, at least, the matchup of Porter against two Pro Bowl linemen isn’t good for Pittsburgh.

WHEN PITTSBURGH HAS THE BALL

The big surprise of the 2005 postseason has been the explosion of the Steelers’ passing game. But except in one specific situation – third-and-long – Pittsburgh’s passing game really isn’t any different than it has been for two years. The Steelers might emphasize the running game, but that running game isn’t as good as people think it is, and the passing game is one of the league’s best.

Because the Steelers are always running the ball, they also throw less often than any other team. That’s why Pittsburgh ranked just 24th in passing offense according to the official NFL rankings, which are based on raw yardage. DVOA, which instead measures things on a per-play basis, ranks the Steelers eighth, and even that ranking is skewed a bit by the four games in which backup quarterbacks Tommy Maddox and Charlie Batch replaced an injured Ben Roethlisberger. Omit those four games, and Pittsburgh’s total offense ranks third behind the Seahawks and Colts.

Despite great overall play, Roethlisberger struggled converting third downs during the regular season. But during the postseason, Pittsburgh’s conversion rate on third-and-long (six or more yards to go) has gone from 28% to an extraordinary 47%.

To put this in perspective, the league average was 29%, and Indianapolis was the only NFL team with a conversion rate above 36%. There is almost no chance that the Steelers can keep this up. That’s a problem, because they end up in a lot of third-and-long situations thanks to a running game that’s nowhere near as good as advertised.

Overall, Steeler running backs averaged 4.2 yards per carry, 12th in the NFL. And they averaged just 3.2 yards per carry when losing or tied, lower than every team except Arizona. Willie Parker began the year with two big 100-yard games, then slowed down, and he’s averaged less than three yards per carry in the playoffs. Jerome Bettis doesn’t just have a low 3.3 yards-per-carry average because he takes the ball in short-yardage situations – he also averaged less than three yards on first-and-10.

The Steelers will find running the ball even harder than usual because Seattle’s front seven is the league’s best against the run according to our adjusted line yards metric, which cuts runs at various lengths to emphasize the importance of blocking in the trenches. The Seahawks also rank fourth preventing conversions on short-yardage runs, and led the league in sacks.

Seattle’s front seven is far better than in years past thanks to health (defensive end Grant Wistrom), smart free agent signings (defensive end Bryce Fisher), and a phenomenal draft (linebackers Lofa Tatupu and LeRoy Hill). But the same can’t be said for the secondary. Cornerbacks Andre Dyson and Marcus Trufant have been inconsistent all year. Safety Michael Boulware was a college linebacker who is very good at stopping the run and covering short passes over the middle, but he can be beaten deep time and again.

Just like Pittsburgh and third-down conversions, Seattle turned its weakness in the secondary into a strength this postseason and shut down two of the best receivers in football – Washington’s Santana Moss and Carolina’s Steve Smith – in successive weeks. Things won’t be so easy against the Steelers. Hines Ward is one of the league’s best receivers, and the Steelers offensive line won’t let the Seahawks get pressure with their front four alone. The Seahawks also have to watch out for tight end Heath Miller, because while NFL tight ends averaged 10.0 yards per reception this season, tight ends averaged 14.5 yards per reception against Seattle.

SPECIAL TEAMS

Seattle and Pittsburgh are basically even in special teams, although each stands out in one specific area. Pittsburgh’s advantage comes on punt returns, where there is always a chance that Antwan Randle El will make a game-changing play. The Seahawks’ advantage comes on kickoffs, where their great coverage will make it just a little bit harder each time Pittsburgh has to try to answer a Seattle score.

OUTLOOK

The Seahawks will get their points and bottle up the Pittsburgh running game. That leaves it up to Roethlisberger to build on his growing legend by passing the Steelers to victory in a shootout. If he plays as well as he did in the AFC playoffs, the Steelers will win. If the Seattle secondary can keep from reverting to its unimpressive midseason form, the Seahawks will win. This is a very close matchup that could go either way, but Roethlisberger can’t keep converting half his third-and-longs forever, and that makes Seattle the favorite.

The Pick: Seahawks

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