There are regular season games that define a season, and the Philadelphia Eagles are sure hoping that yesterday’s 27-3 loss to the Pittsburgh Steelers wasn’t one of them. It will be some weeks before we know what the game said about the Eagles, but for the time being the evidence indicates that the Steelers are for real.

There is no precedent for what the Steelers accomplished the last two Sundays, first whipping the defending champion New England Patriots by two TDs and, yesterday, dominating the NFC’s top team. It was the first time in NFL history that a team has won back-to-back games against unbeaten foes this late in the season.

The win over the Patriots wasn’t totally unexpected – everyone has to lose sometime. The severity of the Eagles’ defeat, though, was mind-boggling. The Eagles ran just 36 plays from scrimmage and rushed for a ridiculous 21 yards on eight carries. They netted just 90 yards through the air. Donovan McNabb, who had been touted for league MVP before this game, was 15 of 24 for 109 yards, an anemic 4.5 yards a pass, and was sacked four times.

On the Steelers’ side of the ball, their sensational rookie, Ben Roethlisberger, was 11 of 18 for 183 yards, a healthy 10.2 yards a throw. That is practically all you need to know about the game: A team that averages 10 yards per throw will beat a team that averages 4.5 yards a throw better than 90% of the time.

Having punched out a 21-3 halftime lead, the Steelers had the luxury of spending most of the second half running the ball while the Eagles scrambled to catch up. The much-discussed loss of running back Deuce Staley proved to matter not at all, as Jerome Bettis was unstoppable.

Relegated before this game to the status of a short yardage backup, the 32-year old running back barged through the Eagles’ front wall for 149 yards on 33 carries. One of the big reasons he was able to do this was that the Steelers bolstered their offensive line with two tight ends, a completely unexpected tactic in a game that everyone thought would be a passing duel decided by the quarterback who hit on the most bombs to his wide receivers.

While the Eagles’ defense spent most of the afternoon laying back and waiting for deep passes that never came, the Steelers battered them running off tackle. The Eagles’ safeties were physically overmatched by the Steelers’ tight ends, and by the time Philadelphia adjusted in the second half by bringing in an extra linebacker, the Steelers already had an 18-point lead.

The Steelers were terrific on both sides of the ball, but it was on defense that the game was essentially won. How they shut down an Eagles offense that had led the NFC in scoring is a question that will be baffling NFL offensive coordinators for the next few weeks.

The Steelers don’t boast a great pass rush, but because they play the run so well, opposing teams have mostly 2nd and 3rd-and-long plays on which to pass against a much-improved secondary. Under veteran defensive coordinator Dick LeBeau, who returned to Pittsburgh this year when Tim Lewis was fired, what the Steelers do best on defense is cover the opposing team’s primary receivers.

Ricardo Colclough and Chad Scott might be the best tandem of young cornerbacks in the league, and on this day they held professional big mouth Terrell Owens to just 53 yards on seven catches, the longest for 20 yards. Owens amassed just 33 yards for his other six catches, the kind of numbers you’d expect to get for dumping the ball off to the fullback.

Up at the line of scrimmage, LeBeau implemented a game plan designed not so much to pressure McNabb as to contain him. A similar strategy has been used around the league with success on Michael Vick and other mobile quarterbacks; the basic idea is to take away the right and left rollout, keep the passer in the pocket, and force him to read coverages.

This is something that, for all his talent, McNabb has never done particularly well. He was tentative and befuddled against the Steelers yesterday; all four of his sacks resulted not from great pressure but from great coverage downfield, which had him pump faking and pump faking before trying to run up the middle. And always too late – perhaps the best running quarterback in the league failed to rush for a single yard.

Play-by-play man Joe Buck caught on quickly to the Steelers’ strategy: “Pittsburgh isn’t exactly jamming the Philadelphia wideouts at the line of scrimmage, but they are disrupting them, pushing them towards the sidelines.” The Eagles never did catch on, which is, sadly, a trademark of Andy Reid-coached teams in big games over the last four seasons.

For the Steelers, the path looks pretty clear. Their only tough-looking games for the rest of the year come against the Jets and Giants on December 12 and 18, and home-field advantage looks like a cinch. As for the Eagles, they still have the NFC’s best record and a more than decent shot at the home-field advantage in the playoffs, but none of their big questions have been satisfactorily answered.

The truth is that for the last few seasons the Eagles have been carried primarily by their defense. The loss of Pro Bowl cornerbacks Troy Vincent and Bobby Taylor still hasn’t been addressed, and the once fearsome pass rush has gone soft. As for the offense, McNabb is no closer to being a big-game QB now than he was three seasons ago, and the Eagles have a potential clubhouse powder keg in Terrell Owens. When you proclaim yourself, in effect, the straw that stirs the drink, you had damn well better stir. Right now, the Eagles are shaken, not stirred.