For a rivalry to exist there must be more between two teams than physical proximity. Each must be a threat to the other's well being. That is what makes a rivalry bloom. That is finally what exists between the Boston Red Sox and the New York Yankees.

For decades theirs was a one-sided rivalry at best, a case of tolerance for the presence of gnats on the one hand and pennant envy on the other. To the Yankees, the Red Sox were an annoyance, a good little team that kept dogging at their heels like a younger brother. The Sox were always around, but for 86 years they were something the Yankees could deal with whenever they had to.

To Boston, the Yankees were the big brother who was always a little bit too strong, a little bit too big, a little bit more developed, a little bit too much to handle. They were the team they chased but seldom caught.

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Maybe the Yankees hadn't won the World Series since 2000, but you can't take much consolation in that when you haven't won it since 1918.

And then the world changed.

Not only did the Red Sox finally win the Series last October, they did it at the expense of the myth of Yankees superiority. To do it, they had to make the Yankees their unwilling co-conspirators in the best of ways, for rivalry's sake. To end an 86-year World Series drought, the Red Sox had to put the Yankees on the wrong end of the worst postseason collapse in baseball history.

Who leads a best-of-seven-game series 3-0 and gets swept four straight? Who leads 3-2 after five games and blows the final two games on their home field, in this case hallowed Yankee Stadium?

Most of all, who lets their greatest rival, the Red Sox, inflict such embarrassment on them?

That is the situation with a new baseball season dawning. After the Yankees' stunning four-game collapse in the American League Championship Series, the offseason became an orgasm of charges and countercharges. Alex Rodriguez, the Yankees' pampered superstar third baseman, went public with a series of slaps at Curt Schilling, who beat the Yankees down with blood leaking through his sock to become a mythic hero all over New England. Trot Nixon, Boston's hard-nosed right fielder, called out A-Rod. Schilling responded in the way you can respond only if you are on top. He said to consider the source.

Consider the source?

Now that's a rivalry.

It only heated up further after Yankees owner George Steinbrenner went after A-Rod, saying he needed to take more of a "leadership role'' in the Bronx this season, implying that he let the Boss and all Yankees fans down last year despite hitting 36 home runs and driving in 106. When you play in New York and are paid $25 million a season, those numbers mean nothing if you can't get your team safely home after building a three-game lead.

It was A-Rod, after all, who cost his team dearly when he illegally slapped a ball out of the hands of Red Sox pitcher Bronson Arroyo at a crucial moment of Game 6 of the ALCS, looking like a spoiled brat cracking under the strain of the kind of moment that has made the Yankees-Red Sox rivalry so compelling the past 30 years.