Every Red Sox achievement must be filtered through the prism of the Yankees’ relative performance, and vice versa. It’s the central dynamic of their wacky relationship.

So, the stunning state of affairs that’s apparent as we pass the first milestone of the long, long season becomes a question of, ‘‘Is it all about how good the Red Sox have been, or is all about how awful the Yankees are.’’

The quick and easy answer is, ‘‘It’s some combination of the two, obviously.’’ But not so fast; it may not be that simple.

Who could deny the Red Sox a soupcon of the credit they deserve? If they continue to play the rest of the season at a .700 clip as they have between April Fool’s Day and Memorial Day, they will win 112 games. In the contemporary era -- since the dawn of the ’90s -- only two teams have done that. One of them being, of course, the Yankees.

At the other extreme how bad have the Yankees been? If they continue to play the rest of the season at a .437 clip as they have between April Fool’s Day and Memorial Day they will win 71 games while losing 91 finishing 24 games behind their pace of a year ago and 41 games behind their arch foes from the banks of the muddy river. Could you handle that, my dear Nation? More important, could King George survive it without being tempted to take a swan dive off the Triboro Bridge?

Poor George! Only the most heartless Red Sox fanatic would wish this mess upon him. Sliding toward his dotage, he roams the heath of the outer Bronx, like Lear himself, bemoaning the shallowness of his flawed and faithless family. The ’07 Yankees have broken George Steinbrenner’s heart, which will come as a bit of a surprise only to those very same and unforgiving fanatics who never believed he had one.

We’ve only cleared the first marker. We’re still deep in the backstretch. But it’s not too early to consider that the Yankees’ shocking tailspin is much more profound than just another “slow start” or “team slump.” It is beginning to look much more like a total breakdown; a bona fide “collapse.” There’s a precedent and it’s almost eerie in the similarity of the particulars.

By 1965, the Yankees’ domination stretching over two full generations had begun to suffocate the entire game. It was popularly avowed that, ‘‘Rooting for the Yankees is like rooting for General Motors.’’ They were the capitalist pigs of sport, foregone conclusions at the beginning of every season and much loathed because of both their fabulous success and haughty eminence.

But in the ’64 World Series an upstart Cardinals team stunned them in seven rough and tumble games. The Cards had some nice veterans -- Curt Simmons, Dick Groat and Kenny Boyer chief among them -- but their core essence was formed by a quartet of exceptionally smart, driven, and intensely athletic black men: Lou Brock, Curt Flood, Bill White, and the extraordinary Bob Gibson. They were supplemented by a soul brother who just happened to be white, Tim McCarver, the catcher. It was a new game that they played and they took it right to the Yankees while literally also taking their breath away. It was not clear until the following season that when the Cards danced off the field that October they left the Yankee’s dynasty, which had rampaged for 45 years, in an utter shambles.

Yet it took awhile for it to sink in. The Yankees stuttered from the start in ’65, aimlessly plodding through April and May. But it was written off as a minor aberration attributable mainly to adjustment problems with the new skipper, Johnny Keane, plus an oddly devilish siege of ailments besetting the venerable mainstays, Messrs. Mantle, Maris, Howard and Kubek. It was only a matter of time before they got rolling, it was widely presumed. The lineup was still reverently termed, ‘‘the best in the world.’’ Strangely flat all season, they finished sixth -- eight games under .500 and 22 games off their previous season’s pace -- with Mantle hitting .255 and Kubek .218, while Maris was missing 115 games.

The next season Tony Kubek retired, Whitey Ford blew out his arm, Johnny Keane got fired, Roger Maris hit .233 and got traded, and Mickey Mantle had 56 RBIs while veering into his long goodbye. They finished in the cellar, losers to the Red Sox in a taut season-long battle for ninth place. They would need a full decade and the arrival of Steinbrenner himself to recover. When great teams go bad, it happens awfully fast.

Without belaboring the point further you can readily detect echoes in the sudden erosion of the current would-be Yankee “dynasty” with chaps like Jason Giambi, Johnny Damon, Bobby Abreu, Mike Mussina and Mariano Rivera in “starring roles.”

Of course, the times are different. Rich teams can now buy their way back to the table in a hurry if they get lucky. But that process is laden with deceit and the Yankees are properly embittered by the rash of free-agent blunders they’ve committed since they last went all the way in 2000. While Brian Cashman is in charge, they won’t go down that road again.

That, obviously, could change at any moment as poor Cashman begins to look like baseball’s version of “The Dead Man Walking.” Whoever succeeds him will probably be goaded by a furiously determined King George to plunge back into the market fiercely with results that are sure to be dire. When in doubt Steinbrenner will always spend, spend, and then over-spend. But if he and his fickle clan wish to guarantee that it takes at least another full decade to recover from this colossal fiasco they can begin by firing Cashman.

I’d say that the answer to the question posed at the beginning of this thesis is that the bigger story is the free-falling of the Yankees. Yes, the Red Sox have played well, jelled nicely as a team, and deserve much credit. But the Yankee’s spinout dramatically lowers the pressure on them while suddenly turning what has long been the toughest division in baseball into the easiest.

It should also be noted that these Red Sox have been much luckier. Yes, they’ve had their adversities but they have been well within the normal and acceptable range. The Yankees run of bad luck, on the other hand, has been nearly ludicrous with two young pitchers being knocked out for the season by line-drives while a third -- a strapping 20-year-old wunderkind -- goes down with a stretched hamstring in the middle of a no-hitter and is lost for two months. And that’s but three examples.

Now they turn desperately to a bloated and nearly 45-year-old legend to rescue them. Under the circumstances, that tactic begins to look pathetic. It has the potential to become the final indignity.

Such strange business! But this is the stuff that happens when, suddenly, the party’s over. More to the point, as Branch Rickey used to say: ‘‘Luck is the residue of design.’’

It’s still early. We’ve only just cleared Memorial Day, the first marker. If I recall correctly, last year, between around Memorial Day and the end of the season New York picked up about 15 games on Boston. If that happens again, it is you my dear citizens of the Nation who will be looking for bridges -- not including the Triboro -- to jump from.

Stay calm, says I. This is not 1978. I know that when I look in the mirror. I also know that when I take a long, steady, dispassionate look at the scene in the Bronx and the roster of the 2007 New York Yankees.