The only sure thing one could say about the American League East divisional race yesterday was that the Yankees wouldn’t end the evening any worse than tied for first place, and that was only because the Boston Red Sox had the day off. In this strangest of races, this is the closest thing to predictability either team has provided in months.

Even on their day off, the Red Sox seemed to create more doubt about their position in the race, having to deflect a report that Keith Foulke was done for the year. At this point, Foulke’s absence is a non-event; given his knee injury and slow recovery, he hasn’t played a key role in the Boston bullpen in months. He has pitched only 6.2 innings all month, allowing seven hits and three runs in low-leverage situations. Boston has already replaced Foulke to the extent that they can – the 2005 version that is. The 2004 version hasn’t been and won’t be replaced until next season at earliest. Still, Foulke’s shutdown, if true, removes even the faint hope that the Red Sox will finish the season with something like certainty in their pen.

In this, the Red Sox are just like the Yankees, but with a significant difference: there is no Mariano Rivera in their pen. The absence of a regular ninth-inning pitcher is not, though, the crux of the problem, but simply the absence of a good pitcher. The Yankees may have the only elite closer left standing, but baseball games are comprised of 27 outs of equal value – the game doesn’t end until all of those outs are made. The way closers are used exaggerates their importance. They pitch in some high-leverage situations, but also often pitch with safe three-run leads.

The only way that the lack of a top closer is a distinct disadvantage for the Red Sox in and of itself is if manager Terry Francona saves his better relievers (Mike Timlin, perhaps Jon Papelbon) for so-called save situations when real crises come earlier in a particular game. Close leads are lost by middle relievers who should only be pitching with large leads while setup men and closers gain weight in the bullpen. For the Red Sox to use plumbers in the middle innings in order to improve their ninth inning outlook would be a great illustration of the cliche about robbing Ringo to pay Paul.

Since Joe Torre does this as well, New York’s advantage in the arms race is somewhat negated. It is worth noting that Rivera has been used more efficiently as the season has gone on – desperation sometimes leads managers to do the things that seemed beyond them under normal conditions – but Torre will never use Rivera in the sixth or seventh inning for fear of being mocked the first time that Rivera prevents the lead from changing hands early only to have Tom Gordon blow one late. It wouldn’t happen very often, but once would be enough to derail the experiment forever and cost the manager his job in the process.

Still, Boston’s relievers have been unmercifully hammered this year, positing an earned run average of 5.35. Non-Timlin relievers have been battered for a 6.17 ERA. Yankees relievers other than Rivera and Gordon have been nearly as inflammatory, posting a 5.27 ERA. The advantage for the Yankees, then, is not in when Rivera is used, but that he exists in the first place.

Boston’s picture on offense is still strong, but as much as David Ortiz has solidified his MVP-bid with a torrid September (.338 AVG/.438 OBA/.789 SLG), there are some key personnel who have lost themselves just as the team needed them most. Edgar Renteria’s bat has had a Flying Dutchman quality all year long, coming and going in long streaks. After batting .342/.391/.479 in August, Renteria has plummetted to .167/.198/.192 in September. Having that kind of offensive vacuum lodged in the second spot of the order has been a major handicap to the Boston effort. Renteria’s slump has compounded that of Johnny Damon, whose injuries have worn him down to .281/.323/.333 this month. Captain Jason Varitek, who drove the team in the first half with a batting line of .301/.367/.525, has cooled to .179/.281/.296 in September. On the whole, Boston is batting .267/.331/.427 this month, which is roughly league average (.268/.329/425).

The Yankees have far fewer slumps to deal with. The team is batting .285/.359/.451 for the month, and Derek Jeter is the only regular who is drastically cold, hitting .259/.333/.383, underscoring a season in which he has made the last out in many games and seriously undermined his reputation as one of the games’ best clutch players. The only other danger for the Yankees is the temptation to play Ruben Sierra, either on offense or defense. As a player who can neither run, nor field, nor hit (he is 4-for-41 this month) Sierra is a triple threat to his own team. Bubba Crosby and Matt Lawton are players with limitations, but they are closer to being useful major leaguers than they are to death, which cannot be said of Sierra.

The most amazing thing about the Yankees-Red Sox race is that the advantage in starting pitching has shifted to New York. With Mike Mussina’s successful return last night, the Yankees suddenly have six viable starters (or, more realistically, five plus Jaret Wright).This may allow for Aaron Small to go to the pen, which could reduce the pressure on Gordon and Rivera while giving Torre an alternative to Tanyon Sturtze, whose ERA has been near 5.00 in the second half. By contrast, Boston’s most reliable starters at this stage are Tim Wakefield and Bronson Arroyo.

That the Yankees would hold all the advantages in this battle seemed impossible only a few weeks ago. There may yet be another reversal, but if it happens it might come too late for the Red Sox.

Mr. Goldman is the author of “Forging Genius,” a biography of Casey Stengel, released this year.