Top five first-half storylines and top five to watch in second half

The major-league season is a few games past its midpoint, and 18 of the 30 teams are within four games of a playoff berth -- eight in the American League, 10 in the National League -- meaning 60 percent of the clubs still have realistic hope of playing October baseball.

But the drama this season is richer than that of simply who will make the playoffs. Herewith are the five top storylines from the first half and five more to look for in the second half.

1. Year of the Pitcher, Redux

Pitchers grabbed all the headlines in the first half. There were four no-hitters, including two perfect games. There are 11 pitchers with double-digit win totals, there are 19 starters with a sub-3.00 ERA and there have been 79 games with 10 or more strikeouts.

At the same point of last season (i.e. the Wednesday before the All-Star Game), there had been zero no-hitters, and there were only seven pitchers with double-digit wins, 12 starters with a sub-3.00 ERA and 64 games with 10 or more strikeouts.

2. Surprise teams

The NL Central-leading Reds have arrived a year or two ahead of schedule, and the NL West-leading Padres have thwarted all common logic. Cincinnati's young core of Joey Votto, Jay Bruce, Drew Stubbs and pitchers Johnny Cueto and Mike Leake was thought to need more seasoning and maybe the addition of Cuban defector Aroldis Chapman, a raw talent still fine-tuning his command in the minors. Instead, the young players have exceeded expectations and been complimented by the surprising Jonny Gomes and All-Stars Brandon Phillips and Scott Rolen. The Reds are leading the Cardinals by two games, thanks to improved defense, fewer injuries and end-of-game resiliency, resulting in a major-league leading 26 come-from-behind victories.

While one of SI.com's experts dared to pick the Reds, none picked the Padres, even though every one of their NL West rivals was selected. San Diego's offense is not very good, having scored only the 23rd most runs in the majors, but it has by far the best pitching (3.05 team ERA) and, when combined with its excellent defense, the best overall run prevention (275 runs allowed, 35 fewer than any team in baseball). That the contributions have come from four of the five starters and the deepest, most effective bullpen in baseball (seven relievers with at least 16 innings and an ERA of no more than 3.10) means that one or two could falter and the Padres might still be able to keep it up.

3. Disappointing teams

The Mariners were a trendy pick to win the AL West, and the Brewers and Cubs were thought to challenge at least for the wild card out of the NL Central. Instead, all three are 10 or more games out of the playoffs. While the Orioles are worse than anticipated, they weren't expected to be good, and the Phillies, though they've underwhelmed, have been treading enough water to remain in contention.

Seattle's trouble is its inability to score. The M's are on pace for 563 runs, which would be the fewest runs since the 1992 Dodgers only managed 548. The Brewers, on the other hand, have already allowed 436 runs and have the fourth-worst pitching with a 4.80 ERA. And the Cubs have been an altogether dysfunctional bunch, whose highly-paid star corner infielders are batting .230 (Derrek Lee) and .184 (Aramis Ramirez) and whose even higher-paid starter (Carlos Zambrano) has twice been banished to the bullpen.

4. Interleague imbalance

The unequal schedules of interleague play can make for a season-resuscitator, especially for AL clubs. The White Sox are 29-35 against AL teams but are only one game off the Central lead because of their 15-3 interleague record, which included playing 15 of its 18 games against sub-.500 NL teams. They swept the Nationals and Pirates, took four of six games against crosstown Cubs and won two of three at home over the Marlins; their sweep of the NL East-leading Braves is undeniably impressive, though that too came at home.

The Rangers went 14-4 in interleague play, while Texas only played sub-.500 teams, with sweeps of the Marlins and Pirates and a 5-1 mark against the Astros. The Angels, meanwhile, had to play six games against the Dodgers and three games against both the Cardinals and Rockies and went 11-7.

The Red Sox improved their standing through interleague play the hard way. Boston went 13-5 while playing 15 of those games against the NL elite: six with Philadelphia and three each against the Dodgers, Giants and Rockies.

The Mets were the rare NL team to get into the act, going 13-5 by sweeping a pair of road series against the AL's worst two teams, the Indians and Orioles. New York played the contending Tigers and Twins at home, missing Minnesota starter Francisco Liriano and seeing Detroit's Justin Verlander knocked out after two innings because of an extended rain delay.

"That's the unfair part of interleague play," said one NL scout. "You can bury a team in interleague play."

5. The continued degradation of the aged

Before the season, the story was that older players like Jermaine Dye, Gary Sheffield, Carlos Delgado, Nomar Garciaparra and John Smoltz couldn't find a job in free agency because of age discrimination -- that teams were increasingly hesitant to sign players in the their late 30s.

Then came the decline of several older players still active in the majors: Trevor Hoffman was displaced as closer; Ken Griffey Jr. retired; and Chipper Jones appeared to be considering announcing that he'd be joining Griffey after the season. Others, such as Todd Helton, Raul Ibañez and A.J. Pierzynski have also mightily struggled.

Of the 78 games mentioned above in which a pitcher has thrown 10 or more strikeouts, only five of them -- two each by Chris Carpenter and Roy Halladay and one by Andy Pettitte -- have been thrown by guys who have celebrated their 32nd birthday. Only 15 of those 10+ strikeout games were thrown by pitchers who were 30.

Of the 94 players who have hit at least 10 home runs, 24 of them have already turned 32, but only 12 are also batting at least .270.

1. Which playoff races will come down to the wire?

Not one of the divisional frontrunners leads by more than four games, and four of the divisions (AL East, AL Central, NL East, NL West) have two other teams within five games of first. The AL Central has set the standard for tight races, having needed a one-game playoff to settle its winner each of the past two seasons, something the NL West needed in 2007. So there has been a 163rd game the past three seasons and each has been a one-run thriller, with two extending into extra innings.

This year's tight races suggest that could happen again and, even if it doesn't, then the schedule-makers' emphasis on divisional play late in the season should keep things exciting. In the AL East, for instance, the first-place Yankees play 13 of their final 19 games against either the second-place Rays or third-place Red Sox.

2. What will happen at the trade deadline?

Mariners' co-ace Cliff Lee is the clear best player among those known to be available, and the Twins appear to be the current favorite, given their ability to offer catching prospect Wilson Ramos to Seattle, which is a key area of need.

If Diamondbacks starter Dan Haren or Phillies right fielder Jayson Werth become available, as some rumors have suggested, they'd be roughly as valuable as Lee, though acquiring Haren -- signed through 2012 with a reasonable 2013 option -- would require trading a lot more talent.

But a major part of the deadline story will be who emerges as a buyer. Most years that's a question of who's in contention, but increasingly there are other factors at play, most notably inability to add payroll or a reluctance to part with prospects. The Yankees, for instance, don't seem keen on trading the necessary young players for a veteran star and will probably instead acquire a bat for the bench (like the Orioles' Ty Wigginton) or a reliever for the bullpen. Relief help is also the direction the Red Sox will take.

So the two biggest spenders may only add smaller parts, while the Phillies, Rays and Twins are among the few teams who have indicated a willingness to add payroll. For various reasons, other contenders -- such as the Dodgers (owners divorce), Rangers (bankruptcy and MLB control) and Mets (financial difficulties) -- will probably stand pat.

3. Will the offenses power up?

Whether it's the aforementioned rise of good pitching or the result of effective tests for performance-enhancing drugs or just an aberration, offense is down this season. Compared to the same point of 2009, runs are down 0.30 per game for both teams and homers are down 0.22 per game.

Those may seem like small amounts, but over the course of a season that's a drop of 729 runs and 535 homers. Given that the rate of runs scored per homer has remained very steady between 1.58 and 1.61 the last few years and 729 runs divided by 535 homers computes to 1.36, then offenses have found a way to replace less than a fifth of the runs lost by the homer drought.

Whether it's pitchers wilting in the heat or balls flying better through warmer temperatures, offenses do tend to pick up in the second half of the season, but not by very much. In 2008 major-league games had 0.11 more homers (for both teams) in the second half; in '09 the increase was only 0.03 homers per game.

4. Who will win National League Rookie of the Year?

Now that we're clear of the Super 2 cutoff and nearly every impactful rookie this season has been promoted, it's become clear that the NL boasts one of the best rookie classes in years. There are those who have been in the majors all season -- Braves right fielder Jason Heyward, Reds starter Mike Leake, Cardinals starter Jaime Garcia, Mets starter Jon Niese, Brewers shortstop Alcides Escobar and Marlins first baseman Gaby Sanchez -- and there are plenty who have made their debuts sometime thereafter: Nationals starter Stephen Strasburg, Marlins right fielder Mike Stanton, Giants catcher/first baseman Buster Posey, Mets first baseman Ike Davis, Pirates third baseman Pedro Alvarez, Pirates starter Brad Lincoln, Cubs shortstop Starlin Castro, Nationals reliever Drew Storen and Giants starter Madison Bumgarner. (Two more rookies, Reds reliever Aroldis Chapman and Phillies outfielder Domonic Brown, have yet to be called up but could have an impact on their clubs' pennant races, though not the Rookie of the Year chase.)

The majority of those rookies are playing for a team still in playoff contention, so a strong half could propel a player to the Rookie of the Year. Of the three current favorites, that's a bonus for Heyward and Leake while the third, Strasburg, won't be pitching meaningful games and may be hampered by the innings limit placed upon him by the organization, which could be about 100 to 110 major-league innings. If Strasburg, currently 2-2 with a 2.45 ERA and 53 strikeouts in 36 2/3 IP, can keep up his current pace, however, he may lap the field, and such disadvantages might not matter.

5. What injured stars will boost their clubs down the stretch?

The return of an injured player is essentially a free acquisition, in that it doesn't require trading prospects or adding additional payroll. Soon after the All-Star break the Mets will benefit from the services of center fielder Carlos Beltran, a five-time All-Star who has missed the whole season after having offseason knee surgery. The Reds will reinstate Edinson Volquez, who has missed a year with Tommy John surgery, soon after the break as well. Neither Beltran nor Volquez has played at the major-league level this year, so there could be a re-acclimation process, especially for Volquez, who won't be received warmly around baseball after flunking a test for performance-enhancing drugs this spring.

Two other NL teams will benefit from the return of 2010 All-Stars, as the Rockies have been missing shortstop Troy Tulowitzki since he broke his wrist and the Phillies lost second baseman Chase Utley to thumb surgery.

And no team has as much talent on the disabled list as the Red Sox, who anxiously await the returns of six former All-Stars -- Josh Beckett, Clay Buchholz, Mike Lowell, Victor Martinez, Dustin Pedroia and Jason Varitek -- of which three were named to this year's game. Of course, given the concurrence of all those players being hurt simultaneously, Boston has a tough chore just staying close enough in the standings to have those returns impact their playoff chances.