In 1978, the Red Sox were 14 1/2 games ahead of the Yankees on August 15th and actually fell behind New York before they managed to force a first-place tie on the last weekend of the season. This was well-prior to the current Divisional Playoff format, and one game with the Bronx Bombers the day after the season ended would decide the American League pennant.
At the time, my two best buds at work were native New Yorkers. Our company had just moved to new facility that weekend and the place was a mess, but someone brought in a TV and we spent the afternoon on the floor watching the Bucky-Bleepin'-Dent game--the Yankee's winning home run produced by a guy who only hit a total of five homers during a mediocre ten-year career.
The Big Apple boys tortured me endlessly on that one. To this day, whenever I see them, we'll hardly get by 'hello' without one of them mentioning it. "Hey, Bill... remember sitting on the floor watching the '78 playoff. Bucky Bleepin' Dent. Who could believe it?"
With just over 20% of the 2007 season now in the stat sheets and only an 8 game lead, we have historical reasons to look over our shoulder.

That said, 'when you're hot, you're hot'; and right now the Beantown Gang is torrid. Yesterday they came up in the last of the ninth trailing 5-0. The hits, errors and fortunate accidents kept coming, capped by a Julio Lugo bases-loaded slow bouncer the Orioles missplayed into the tying and winning run.
I was impressed by the show of emotion, elation, from the Red Sox players who rushed the field... slappin' fives and pattin' asses. They looked like kids, was what it was. As Major League Baseball looks more and more corporate and star players gross more than the GNP of some small countries, a professional team acting like kids can be a good thing: an edge, provided you use it right.
I credit Tito Francona for this, in large part. Oh, he manages the game pretty well, but he also manages the buzz around the team and the mental-health of his players, guiding them by example on how to deal. Now, after a few years under his belt, he's read the whole book on the Boston fans and their phantom menace, the Hub media. There's a lot you can't control, but some you can. Patriots' Bill Belichick survives by saying as little as possible and raising high walls around his private football Fort Apache. Francona is just as effective, but accomplishes it by being open, honest, accessible, and likeably human.
How long can it last? Right now the L family plans our day around the games so we can watch the kids play ball.
