“Break up the Yankees” was the cry after the Joe DiMaggio-led Bombers won straight championships between 1936 and 1939. In an effort to stop the Yankees from improving or replenishing their dominant team, the American League even briefly adopted a rule saying that no team could trade with the previous season’s pennant winner. The rule was misguided, since the Yankees largely built from within in those days; it took until World War II to accomplish what the rule was intended to, and then only temporarily. With the 2008 pennant race all but over for the current roster, it is once again time that shouts of “Break up the Yankees” be heard across the land — but this time they should come from inside the Yankees organization.

There is nothing left for the Yankees to prove in 2008. They’ve established themselves as one of the weaker sisters in club history, not a bad team, but not a good one, either. Before last night’s action, they stood third in the AL East, trailing the first-place Rays by 11 games. They also stood third in the wild card race, 6.5 games behind the Red Sox and 5.5 games behind the Twins. With just 37 games remaining on their schedule, 27 of them not just against clubs with winning records but teams likely headed to the postseason, the Yankees face a nearly impossible task. Add in a lackluster stretch drive in which the club has gone 8-14 with a 5.71 ERA since winning eight straight against the A’s, Twins, and Red Sox at the end of July, and the inevitability of the Yankees taking October off for the first time since 1993 becomes apparent. What’s worse is that judging by the way they’re playing, the Yankees know it, too. They may not have been mathematically eliminated, but they’re not far off from being emotionally eliminated.

With this season over, it is time for the team to turn its attention to next year, a season that could easily be worse than this one. The Yankees will have just three offensive players with any long-term viability under contract: Alex Rodriguez, Xavier Nady, and Robinson Cano. Even this small grouping is suspect and should probably be restricted to A-Rod alone. Nady is having a belated peak season, and if he regresses to his career rates (.272 AVG/.327 OBA/.441 SLG coming into the season), he will return to being a very average producer for a corner outfielder. As for Cano, the temptation here is to dismiss his incredibly poor April as a fluke and consider his .299/.332/.442 in 93 games since then as evidence that the Cano who so excited in 2006 and 2007 will be back next year. That said, even within those 93 games, Cano has been on a roller coaster of feast and famine, so a cold finish would throw that conclusion into doubt.

The Yankees also have their trio of 34-year-olds who, to paraphrase Casey Stengel, have a good chance of being 35 next year. Therein lies the problem. Hideki Matsui and Johnny Damon have hit well when healthy, while Derek Jeter has had a season that has so far been disappointing by his own standards, while falling short of outright disaster given the general weakness of the shortstop position; AL shortstops are hitting just .264/.316/.371, so Jeter is still an offensive plus relative to the competition, even if he isn’t the MVP candidate of old. The problem is that another year older means an even greater likelihood of one, two, or all of these players disappointing due to age-induced decline, injury, or both. Just ask Jorge Posada, also under contract, about that. Nor will the defensive skills of these three players, which currently range from questionable (Damon) to tolerable (Jeter) to excused with a doctor’s note (Matsui), get any sharper. The Yankees and top-flight defense have been estranged for a long time, with the club currently ranking toward the bottom of the majors (tied for 24th) in turning balls in play into outs. There won’t be a reconciliation next year.

The players who replace likely free agents Bobby Abreu and Jason Giambi had better be very good, and Mark Teixeira can’t do the job by himself, if the Yankees even get him. As for bringing back Abreu or Giambi, it’s a bad idea, even if Giambi’s option wasn’t insanely expensive. It’s a question of age and defensive utility, just as it is for the other vets.

With next year’s pitching staff likely to be at least as unsettled as the current edition, the Yankees are in a difficult spot. If baseball teams don’t decide when to rebuild, the gods of baseball tend to decide for them. There’s a penalty to holding on too long, to having the issue forced: Your team might turn into the Baltimore Orioles (in the Yankees’ case, Jeter standing in for the aging Cal Ripken). Hence, the Yankees should be broken up now, by Brian Cashman, with the veterans sent out of town by August 31 for the best offers available.

Mr. Goldman writes the Pinstriped Bible for yesnetwork.com and is the author of “Forging Genius,” a biography of Casey Stengel.