The All-Star break might be seen as a time to rest and celebrate stardom at the Midsummer Classic, but what it really represents is a pause that gives teams the opportunity to take stock of what kind of season they’re having. In particular, they can gauge whether they have a shot at contending, and, perhaps most important with regard to longterm planning, whether they should be buyers or sellers at the end of this month. This can mean dealing talent for prospects to help retool for a club’s next serious bid, or patching up that gaping hole or two on the roster that might keep a team from making the serious money that comes with playing deep into October.

In the American League, a changing dynamic as far as who makes it can already be seen. Gone are the days when you could assume that the Yankees and Red Sox had the AL East title and Wild Card locked up between them. The AL Central has had four teams, with the exception of the hapless Royals, make playoff runs in the last three years, while the AL West has seen the A’s and Angels trade off division titles since the Mariners’ record-setting 116-win title in 2001. As a result of having produced five different pennant winners in as many years, the American League is in the midst of the liveliest competitive environment it has seen since the 1980s. Then, eight different pennant winners emerged between 1981 and 1988. This year there are even pretty good odds of a sixth in six, with the Indians and Mariners boasting the best chances of making it so, if also representing a nightmare for network programmers.

In the AL East, the failure of the Yankees to rise to the challenge of Boston’s aggressive assembly of what appeared — at least initially — to be the league’s best ballclub has already killed plenty of trees this spring. The mounting injuries in the Bomber’s rotation, the repeated setbacks among the various stars in the lineup, and the criminal failure to find an adequate first baseman this past winter have all combined to seemingly bury the club’s expectations. However, despite these numerous problems, the Yankees still have a 1-in-6 chance of making it to the playoffs, and that’s without anticipating the benefits of getting Philip Hughes back in the rotation or of adding a major league-caliber bat to patch up the number of runs the Yankees are losing at first base relative to their rivals.

How did the Baseball Prospectus crew come up with 1-in-6, especially given the amount of despair surrounding the Yankees? The founding seamhead of the baseball analysis think-tank, Clay Davenport, sits down to calculate each team’s performance in the season thus far, makes some allowances for the schedule it has played to compensate for their strength of opposition, and some for its expected performance for the remainder of the season. Because the Yankees have drawn a lot of matchups against Boston in the first half, but have a lot of games remaining against teams like the Devil Rays, the Bombers have cause for optimism.

This is in contrast to the Toronto Blue Jays, who despite being tied with the Yankees, actually face steeper odds of catching the Red Sox or winning the Wild Card. With 14 more games to play against the Yankees and 10 to go against the Red Sox, plus several tough swings through the AL Central and AL West, the Jays are in a far worse position from here on out. All that doesn’t even take into account whether the team will resolve its problems in the rotation, let alone find a left fielder or a shortstop that can contribute on offense. It isn’t impossible, but on the strength of the talent at their disposal, and with the schedule they have yet to play, when Davenport runs a million seasons to see what that tells us about the likely outcome, the Blue Jays have come back from this far behind only 3% of the time.

What about the races in the Central and the West? The Detroit Tigers seem to be the prohibitive favorite to repeat for the division title, but that’s partly a matter of scheduling and a result of the conclusion that they should be much stronger with Kenny Rogers in their rotation instead of Chad Durbin. The team will also have the benefit of deciding what to do with rookie fireballer Andrew Miller in the second half. Factor in a better lineup than the one the Tigers used to win last year’s pennant — thanks in no small part to the addition of Gary Sheffield — as well as a creeping recognition that Sean Casey doesn’t walk on water, and you’ve got a team very well-equipped to mount a pennant defense. The Indians were the unsurprising sleeper pick of a lot of statheads, but they addressed the problems they knew they had after last season: improving their pen and infield defense, getting shortstop Jhonny Peralta in shape, and developing depth to adapt to the non-performance of outfield veterans like Trot Nixon and David Dellucci. If Jake Westbrook and Cliff Lee can get more fully on track in their comebacks from injury, the Tribe will have a rotation that can run with the Tigers, making them a solid favorite for the Wild Card.

In the West, if there’s an upset, it’s that the league’s best rotation hasn’t been enough to compensate for a weak lineup. Pitching and defense wasn’t supposed to be the Moneyball franchise’s mantra, but those are the strengths of an A’s club that needs better work from its injury-plagued pen and from a similarly handicapped offense. Nevertheless, the defending AL West champions have a 1-in-7 shot, which ranks behind the prohibitively favored Angels and a surprisingly solid Mariners club. Still, this is the Angels’ division to lose, and with a rotation that runs perhaps seven deep plus a lineup gifted with power, speed, and an aggressive approach instilled by the organization, it’s hard to see how they could avoid unseating Oakland.

Ms. Kahrl is a writer for Baseball Prospectus. For more state-of-the-art commentary, visit baseballprospectus.com.