The unknown: What's in store for second half?

The unknown: What's in store for second half?

If you need a reminder that the midway point of the season is little more than a checkpoint, look no further than the defending champion San Francisco Giants. Or perhaps ask the 2010 Padres and White Sox about their division leads at the All-Star break.

Yes, history has shown that first-place teams at the break are all but guaranteed to make the playoffs. And sure, no team more than five games under .500 at this point has ever stuck its foot in postseason's door. But if last year was any indication, that doesn't mean the second half of this season will be devoid of drama.

At the 2010 All-Star break, San Francisco was barely keeping its head above water, owning a 47-41 record and a fourth-place standing in the National League West. Then, of course, the Giants went on a remarkable run to their first World Series title since moving to San Francisco.

On the other hand, Atlanta, San Diego and Chicago led at the conclusion of the first half but two of them fell short of the playoffs, the Braves holding on for the Wild Card. The 2010 Yankees, leading the Rays by two games at the break, settled for the American League Wild Card. Of the midway-point division leaders a year ago, only two -- Cincinnati and eventual AL-champion Texas -- finished in the same spot.

Which brings us to this year, when many of the usual suspects have been joined at the top of the heap by a few unexpected guests.

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With the 2011 All-Star Game in the rear-view mirror, the usual questions come to the forefront. Can the leaders stay hot? Can the early surprises keep it up? Can any of the clubs on the fringe make a late push?

But after a second half like last year's, perhaps the most important question isn't a matter of "can" but just the opposite: Can't anything happen?

Here's a look at how the postseason races are shaping up by league:

AMERICAN LEAGUE
Stop us if you've heard this one before: The Red Sox and Yankees are in position to take a close AL East race down to the wire, and the low-payroll Rays are within striking distance to set up another three-way battle for two playoff spots.

Sounds familiar, right? Well, settle in for more of the same.

They will have plenty of chances to separate themselves, especially in the final weeks of September. The Yankees and Red Sox will meet nine times, including three games in the Bronx on Sept. 23-25. Each team will also play 13 second-half games against the Rays, who have overcome the loss of several key players to remain in contention.

With the exception of the AL West-leading Rangers (.554), the three highest win percentages in the league are held by the Red Sox (.611), Yankees (.602) and Rays (.544), and the greatest run differentials in baseball are owned by New York (121) and Boston (111). The next-highest run differential in the AL? Texas, at 53.

The AL Central might not be home to the marquee matchups, but the Tigers and Indians will come out of the break involved in the tightest race in the league. While the Indians have been one of the biggest surprises this season, the real question at this point seems to be whether the Tigers can maintain their pace.

Not only has Detroit allowed more runs than it has scored, seemingly an unsustainable method of success, but the Tigers don't have a great track record of second-half success. The last three years combined, they went 143-124 before the break but 96-112 the rest of the way. They will need to do better to hold off the Indians, White Sox (five games back) and Twins (6 1/2 games back and winners of nine of their past 12).

Finally, the AL West already appears to be a two-horse race between the Rangers and Angels, who sit only one game behind Texas. They split their six first-half games and will square off 13 more times, including the final series of the season -- a three-game set in Anaheim.

Working to the Angels' advantage: They will see much less of the top AL East teams than their division rivals. The Rangers still have seven games against the Red Sox and seven more with the Rays, while the Angels will take on the Yankees six times to complete their East slate.

As exciting as the other two division races will shake out, similar storylines will likely shape the AL playoff race. New York will add key pieces but battle injuries. Boston will rely on familiar stars and new additions. And Tampa Bay will rely on pitching and creativity and good timing on offense.

But when it comes to the Wild Card race, look to the East -- as repetitive as that view might feel by now.

NATIONAL LEAGUE
Barreling toward the most critical stretch of the season, the answers to the following four questions will likely decide the NL races.

Is the Giants pitching good enough to pick up their struggling offense and hold off the D-backs in the West? Are the Pirates for real? Do the Cardinals have what it takes to pull away from the pack in the Central? And perhaps most important, will anyone score enough runs against the Phillies and Braves for any of that to matter come playoff time?

The NL East features the two most dominant pitching staffs in the Majors -- the first-place Phillies and the Braves, who sit 3 1/2 games back but are in prime position to control the Wild Card race with a 54-38 record. Philadelphia has allowed a Major League-low 295 runs; the Braves are barely trailing with 312. The two have split their season series and will meet six more times, including a season-ending series in Atlanta.

The Phillies' .626 winning percentage is the best in baseball, and as expected with their starting rotation, they appear to be the early frontrunners to represent the NL in the World Series.

But crazier things have happened, and look no further than the NL Central for proof. The Pirates, over .500 at the break for the first time since 1992, will be looking to prove their 47-43 first-half record wasn't a fluke.

The Brewers, tied for first in the Central with the Cardinals and having acquired Francisco Rodriguez from the Mets on Tuesday, have two things working against them: a minus-1 run differential and a subpar road record (16-29). St. Louis appears to be the logical pick to win the Central, owning a positive run differential and a far better track record. They will certainly be tested in September, though, enduring a grueling stretch against the Reds, Brewers, Braves, Pirates, Phillies and Mets.

And don't count out the Reds, either. Last year's Central champs can outhit anyone, leading the NL in runs, and might be on better footing if not for a few prolonged stretches of poor play.

Out West, San Francisco rode its usual combination of strong starting pitching, a lockdown bullpen and just enough offense to a first-place 52-40 record. Following several critical first-half injuries, the Giants might need to pull off a trade or two to boost their slumping lineup. And they could used some help, as the surprising D-backs aren't far behind at 49-43.

The two will meet nine times in August and September, including in the second-to-last series of the year in Phoenix, but that might work to the Giants' advantage considering their 7-2 record against Arizona.

Then again, if the NL West taught us anything last year, it's to expect the unexpected.

Adam Berry is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.