This is why they play the games: so you can see things you’ve never seen before.

Baseball Prospectus has shown that a team’s final record will generally be quite similar to its record after 30 games. This means teams and fans have something in common: the thirty something blues. By that age – or at that 30-game point in the season – you pretty much are what you’re going to be. Whether this is something to mourn or celebrate depends on the team and the person.

In the case of baseball teams, just one ball club between 1930 and 1999 opened the season 11-19, as the Yankees did, and made the playoffs.

If a team hasn’t found itself after 50 games, it probably never will. The Yankees were 27-23 at game 50, good for a .540 winning percentage. This isn’t bad, but it’s generally not enough to win a division. By this same theory, the record at the halfway point should be ironclad and inescapable. At 81 games, the Yankees were 42-39 (.519). Things had gone backward from the 50-game mark.

At that moment, it would have been quite reasonable to declare the Yankees down for the count (as many did, including this columnist), yet as of Monday, they had surpassed the Red Sox and taken first place in the AL East. The short, superficial version of why this happened is that the Yankees got hot and started July with an 11-3 record, while the Red Sox simultaneously pancaked at 5-10. Since three of the Yankees’ 11 wins came at the expense of the Red Sox, they made more rapid progress than they otherwise could have.

On a deeper level, Boston has several problems that are going to be difficult to correct. While the offense has walked as often as ever in July, leading to a good on base percentage (they have taken nearly two walks for every one by opponents), the team’s batting average is stuck at .250. More significantly, more than half the starting lineup has lost track of its home run stroke.

Bill Mueller, Kevin Millar, Edgar Renteria, Mark Bellhorn, Johnny Damon, and Jason Varitek have combined to hit three home runs so far in July. Of these, only Varitek and Millar can even be called power hitters, so this segment of the lineup is not likely to start blasting the ball out of the park on a regular basis.

As the trade season heats up, both the Yankees and Red Sox will compete for one more bat at the first-base corner. The Yankees need a guy to play first base or be a designated hitter (wherever the rejuvenated Jason Giambi is not), while the Red Sox need to replace Millar, who has slumped all season in the power department – first basemen are not paid to put up a .384 slugging percentage.

The Red Sox may be able to heal their offensive problems more easily than fill the deficits on their pitching staff. The bullpen has an ERA of 5.43, and with Keith Foulke out, is headless (with the way Foulke was pitching, this may have been a lucky break).Yesterday’s release of lefty spot reliever Alan Embree is only the beginning of what will have to be an aggressive reliever reload.

On the New York side, the Yankees will be hard-pressed to continue to outscore their putrid pitching and defense. This month, the batters have scored nearly seven runs a game, an 1,100-run pace over a full season. The batters are good, but not that good.

The pitching, with a 5.63 ERA on the month, may in fact be that bad. Middle relief is nonexistent. The starting rotation is still guesswork after Randy Johnson and Mike Mussina. Kevin Brown was understandably rusty after eschewing his rehab for an emergency return to the majors, but whether he reverts to anything like even his pre-injury self remains to be seen.

Al Leiter might have been a wonderful fluke. The odds against Aaron Small holding the fort long enough for Carl Pavano to return are approximately 17 billion to one. The odds against Small holding the fort long enough for the beer men to sell out today’s first tray are approximately 12 billion to one. The odds of Carl Pavano holding the fort until Carl Pavano finds last year’s stuff are approximately 10 billion to one.

Right there – before the lack of a center fielder who can catch the ball is addressed, the aforementioned DH is acquired, or yet another two middle relievers can be found (who would have thought the Yankees would ever reach a point where the return of Felix Rodriguez would be looked upon as a godsend?) – you have the makings of an arduous stretch run.

Neither the Yankees nor the Red Sox are quite what they look like this month. The Yankees are not as good as .750, the Red Sox not as bad as .333. The race will almost certainly be determined by the changes they make at the end of the month and, no doubt, by the six meetings left between the two teams.

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