Click here for the American League second-half previews.

Washington Nationals

Second-half key: What, other than monitoring Stephen Strasburg's innings limit? Despite injuries that limited Mike Morse, Jayson Werth and Wilson Ramos (out for the year) to a combined 85 games, the Nationals managed to rank ninth in the NL in runs scored thanks to solid production from Ian Desmond and Adam LaRoche and the emergence of rookie phenom Bryce Harper. They need all three of those guys to keep it going and hope Morse and Werth (once he returns) produce as well.

Player to watch: Ryan Zimmerman signed a $100 million contract extension during spring training but has produced an uninspiring .243/.306/.386 line. That's barely replacement level, let alone what you expect from a guy still owed at least $116 million through 2019. Yes, he's played through a sore shoulder, although after a recent cortisone shot, he hit five home runs in the 12 games before the All-Star break. If the shoulder can hold together and he keeps hitting, the lineup looks a lot stronger.

Best case: The starting rotation remains dominant, Zimmerman keeps hitting, Morse starts hitting like 2011, Werth returns ... and the Nationals find a way to keep Strasburg's innings down as they get ready to start him in Game 1 of the NL Division Series.

--David Schoenfield

Atlanta Braves

Second-half key: At this point the Braves have only two starting pitchers they feel particularly comfortable with: Tim Hudson and Tommy Hanson. So finding more consistently good outings from the 3 to 5 spots in the rotation is key. Jair Jurrjens has had decent results, though his stuff has not been particularly inspiring. Mike Minor and Randall Delgado seem to constantly be undone by one terrible inning. Ben Sheets has looked decent in Double-A rehab appearances but is obviously far from a sure thing. The Braves likely will trade for an additional starter.

Player to watch: If Minor can put his single-inning mental lapses behind him and pitch to the flashes of brilliance he has shown, the Braves would have a lot of their problems solved. Having three dependable starters is a world of difference from having only two. Minor has the stuff and has shown the toughness, at times, to be a reliable No. 3 starter. If he continues to struggle, the Braves may be forced to make a trade they otherwise wouldn't want to make.

Best case: The Nationals shut Strasburg down and the Braves slowly reel them in, with good pitching and offensive performances from Minor, Jonny Venters, Brian McCann, Freddie Freeman and Dan Uggla, while continuing to get the superb efforts they've received all year from Michael Bourn, Jason Heyward, Martin Prado, Hudson and Craig Kimbrel.

--Franklin Rabon, Capitol Avenue Club

New York Mets

Second-half key: The big issue will be shoring up a bullpen that owns an NL-worst 4.94 ERA. No, getting Frank Francisco back from the DL isn't the answer. Led by R.A. Dickey, the rotation had a strong first half (third in the NL in ERA), but with Dillon Gee now out with a blood clot, the Mets may have to turn to rookie Matt Harvey, the seventh overall pick in the 2010 draft who has a 3.39 ERA at Triple-A while averaging a strikeout an inning.

Player to watch: Ike Davis somehow has 49 RBIs despite a meager .201/.271/.388 batting line. Davis had a big June (six homers, 24 RBIs, .563 slugging), but the Mets have struggled against lefties, and Davis' .163 average is part of that problem.

Best case: Dickey has another monster half, Davis and Jason Bay start producing against left-handers, Terry Collins continues to pull all the right strings, the Mets trade for a couple of relievers and the team somehow sneaks in and grabs one of the wild cards.

--David Schoenfield

Miami Marlins

Second-half key: With Giancarlo Stanton sidelined for at least the next month, it's vital for Hanley Ramirez and Jose Reyes to carry the Marlins' offense. The addition of Carlos Lee could prove to be beneficial, but it starts with the team's core of the aforementioned duo. If the Marlins have any hopes of contending, they need to get hot right away.

Player to watch: Justin Ruggiano has been on fire the past few weeks and looks to be getting more playing time while Stanton is out. He doesn't possess much power or upside, but he can definitely hit. The Marlins have been a much better team while he has been hot.

Best case: Stanton comes back to join a hot-hitting duo of Ramirez and Reyes and the Marlins inch closer to the Nationals and Mets by nailing those pesky divisional games.

--Dave Gershman, Marlins Daily

Philadelphia Phillies

Second-half key: The Phillies are already out of it, so their biggest key is getting a good return on the players they ship out, which may include franchise stalwarts Shane Victorino and Cole Hamels. Both are eligible for free agency after the season, and with the new collective bargaining agreement that changed the free-agent compensation rules, the Phillies will be pressured into getting maximum value in trades.

Player to watch: Carlos Ruiz. May as well focus on the most heartwarming story now that their playoff hopes are virtually dashed. The Phillies signed Ruiz out of Panama back in 1998 for $8,000, so you can understand the surprise and excitement around his season. He currently has a 166 OPS+, a mark that has been matched or surpassed by only four other catchers in history: Mike Piazza twice (1995, 1997), Joe Mauer (2009), Mike Grady (1904), and Johnny Bench (1972).

Best case: The Phillies sign Hamels to a contract extension, play a healthy amount of interesting, enthusiastic baseball in the remaining three months, and don't get hoodwinked in any trades.

--Bill Baer, Crashburn Alley

Pittsburgh Pirates

Second-half key: Neil Walker. The Pirates had a very up-and-down first half. Pedro Alvarez and the back end of the rotation probably will have an up-and-down second half. GM Neal Huntington may or may not be able to add a hitter to protect Andrew McCutchen. Walker needs to be the anchor that holds the Pirates' ship steady in the second half.

Player to watch: McCutchen. He might be the most watchable player in baseball, and his first half (.362/.414/.625) puts him on the short list of NL MVP candidates. Another half like that would put the Pirates in the playoffs and cement his reputation as one of the game's elite players.

Best case: Another half just like the first, not only from the Pirates but the Cardinals as well. Erasing the stink of 19 consecutive losing seasons with a playoff berth would be the icing on the cake. Or the pie, in this case delivered in grand style by A.J. Burnett.

--John Franco, Pitt Plank

Cincinnati Reds

Second-half key: While the pitching has been consistently good, Cincinnati's offense has been hampered by an inability to get on base. Dusty Baker's leadoff hitters have combined for a paltry .243 OBP; it is imperative the Reds get more runners on base for Joey Votto and Jay Bruce. The key, perhaps, is Drew Stubbs. At age 27, he is posting career lows across the board (.215/.286 /.367). If he's ever going to show the talent that made him a first-round pick, the second half of this season would be a good time to do it.

Player to watch: Scott Rolen. In the past two seasons, when he isn't injured, Rolen has hit .220/.266/.365 with a 68 OPS+. His fielding remains spectacular, but he has difficulty getting around on fastballs these days. Baker recently called out fans for wanting to see Todd Frazier play more, but the fans have a point. Frazier is hitting .278/.345/.556, and he's outproducing a more-heralded rookie (Bryce Harper). If Rolen can return to form, he will help the Reds. If Rolen's Hall of Fame-caliber career is finished, however, his presence in the lineup will continue to drag down the offense.

Best case: The Pirates remember they are the Pirates (and drop back in the standings), the Cardinals continue to struggle, and the Reds win the NL Central.

--Chad Dotson, Redleg Nation

St. Louis Cardinals

Second-half key: For the Cardinals to return to the playoffs, they'll need their starting rotation to hold up. The silver lining in the news that Chris Carpenter had to undergo season-ending surgery is that it clarifies the situation for GM John Mozeliak, who may want to bolster a rotation that includes a revived Adam Wainwright and a surprisingly dominant Lance Lynn, but who is basically a rookie. And Jaime Garcia, who had a 3.6 WAR for the world champs last year, won't return from the DL until August.

Player to watch: Lance Berkman. He plans to return after the All-Star break, which is only good news for an offense that is tied with the Rockies for best wOBA in the league. Big Puma's availability gives Mike Matheny the opportunity to keep Carlos Beltran fresh while rotating Allen Craig into the mix.

Best case: Cardinals seize the division as Yadier Molina continues his career year and Beltran, Rafael Furcal and David Freese finish the year avoiding the disabled list.

--Matt Philip, fungoes.net

Milwaukee Brewers

Second-half key: The Brewers have to get out to a fast start if they want to compete. They open with St. Louis, Cincinnati and Pittsburgh, a stretch that will determine whether they are buyers or sellers.

Player to watch: Rickie Weeks. Weeks hit just .199 in the first half, but at least he walked a ton -- 45 times -- keeping his OBP at .314. In his past 25 games, Weeks is hitting .284/.352/.463. He'll need to carry that kind of performance through to the second half.

Best case: A 7-2 (or better) opening to the second half carries the Brewers back to .500 and into the division race.

--Jack Moore, Disciples of Uecker

Chicago Cubs

Second-half key: The Cubs need to grow in a lot of directions and fast, and one of their primary areas of concern is quality pitching. In particular, they need to see continued progress from Travis Wood and Jeff Samardzija. Ryan Dempster looks to be on his way out of the North Side any day now. Matt Garza might not be far behind. If Wood and Samardzija can build on the success they had in the first half and develop into consistent, reliable starters, the Cubs' pitching cupboard might not be as bare as it once seemed.

Player to watch: Although he's been with the team a scant 12 games, hard-hitting wunderkind Anthony Rizzo has lived up to much of the considerable hype that preceded him (.354/.367/.688; 4 HR, 4 2B, 9 RBIs). The big question is whether he can carry that performance into Week 3 of his Cubs career and beyond. If so, the team should have another key building block to put alongside Starlin Castro. And if nothing else, the two young phenoms should give fans a reason to tune in.

Best case: The Cubs finish the season better than they started it -- maybe even playing .500 ball the rest of the way -- and head into the offseason with more answers than questions (or at least more than last year).

--Jeremiah Johnson, The View from the Bleachers

Houston Astros

Second-half key: Through the first two months, the bullpen was a strength. As of May 24, the Astros were 21-23 and the bullpen boasted a 2.88 ERA (third-best in the NL) and 1.19 WHIP (second-best in the NL). Then they nicknamed themselves The Regulators and started regularly giving up lots of runs. From May 24 to the All-Star break, they put up a 6.35 ERA and 1.67 WHIP to finish the half with the fifth-worst ERA and WHIP in the league. Not incidentally, they went 12-30 in that stretch and finished the first half with the league's worst record. The bullpen has to start pitching more like it did in April and May for the Astros to have a prayer of not finishing with the league's worst record for a second straight season.

Player to watch: Wandy Rodriguez, and not just for the trade rumors, though that might be reason enough. He's a strong second-half pitcher on a team seriously lacking in good starting pitching. His career second-half ERA is 3.86 (compared to 4.11 in the first half) and his WHIP is 1.29 (compared to 1.38 in the first half). Look for good performances from him as the Astros continue to look to deal their best remaining trade chip.

Best case: The Astros deal Wandy and maybe even Jed Lowrie for solid prospects and position themselves for a second straight No. 1 overall draft pick as they continue to rebuild. Maybe next year.

--Austin Swafford, Austin's Astros 290 Blog

Los Angeles Dodgers

Second-half key: Keeping Matt Kemp and Andre Ethier healthy while also getting contributions from others in the batting order. Though the Dodgers largely relied on Kemp and Ethier during their strong start, those two were augmented by contributions from such lower-profile players as A.J. Ellis and Mark Ellis.

Player to watch: Chris Capuano. He has ascended to No. 2 status in the Dodgers' rotation with an adjusted ERA+ of 131, according to Baseball-Reference.com -- far better than his previous high, achieved in 2006. The Dodgers need Capuano, who turns 34 in August, to sustain much of that excellence through the second half -- or find another source who can match it.

Best case: Kemp and Ethier boost the Dodgers to their April-May form, a July trade acquisition shores up one or more obvious weaknesses, and the Dodgers don't look back in winning the National League West.

--Jon Weisman, Dodger Thoughts

San Francisco Giants

Second-half key: It's hard not to look at Tim Lincecum as the Giants' second-half key. His struggles have been crushing and numerous: He's throwing slower these days, having trouble pitching out of the stretch, and his command, something that was once an improved asset, has slipped. The Giants' offense still looks middle-of-the-pack, and the team will need every ounce of its pitching to contend.

Player to watch: Buster Posey's return has gone better than anyone could have expected. We've all seen replays of the horrific injury that Posey suffered last year in a home-plate collision against the Marlins, but what Posey's been able to do with the bat (.289/.362/.458) while coming back from that injury has been nothing short of incredible. The Giants need to be careful with his workload, because as Buster goes, so go the Giants.

Best case: Lincecum rights his ship, the team stays healthy, and the outfield, led by Melky Cabrera, continues to be an asset.

--Chris Quick, Bay City Ball

Arizona Diamondbacks

Second-half key: With Daniel Hudson out and Ian Kennedy not as dominant as a season ago, rookies Wade Miley and Trevor Bauer may have to headline the rotation. Miley was an All-Star but struggled in his final two starts before the break, and Bauer has just three big league starts.

Player to watch: Justin Upton. A disappointing first half (.273/.353/.401) has led to his name being mentioned in trade rumors. It would take a huge haul to pry away the 24-year-old right fielder, but this isn’t the first time his name has popped up as possible trade bait. Either way, he has to deliver in the second half.

Best case: The Dodgers fall back, Tim Lincecum continues to struggle, Bauer contains his walks and the D-backs sneak in as NL West champs.

--David Schoenfield

San Diego Padres

Second-half key: Their farm system doesn’t have a Mike Trout or Bryce Harper, but they do have plenty of next-tier prospects who should see big league action in 2013 or 2014. So, while waiting for their hospital ward of disabled talent to get discharged, they must decide which of their current players will join the prospects for their next shot at contention in the NL West.

Player to watch: Chase Headley/Jedd Gyorko. With 3B Jedd Gyorko continuing to rake his way through the Padres' farm system, the 28-year-old Headley very well could be on the trading block. He won't hit free agency until 2015. He has a career .811 OPS away from Petco (.848 in 2012) and has a solid glove. There is a paucity of quality third basemen on the market right now (if Toronto falls further out of the race, Edwin Encarnacion also would be a hot commodity), and there are enough contenders with issues at third that his trade value might never be as high. While he’s not a superstar, the Padres could probably be happy getting something half as good as what they got for Mat Latos in return for Headley.

Best case: Headley remains healthy, gets dealt for a near-major-league-ready package, and the September call-ups re-energize the fan base going into 2013.

Diane Firstman, Value Over Replacement Grit

Colorado Rockies

Second-half Key: The Rockies have to find at least a little rotation stability. This season is obviously lost, but a little progress, both on the mound and in the field, would give the Rockies something to build upon in 2013.

Player to watch: Drew Pomeranz hasn’t given up an earned run in 12 1/3 innings since being recalled from Triple-A. It is imperative that he continues to progress. That probably means he needs to be taken off a 75-pitch limit and allowed to go deeper into games when he is pitching well. Placing that kind of restraint on him likely would stunt his development.

Best case: Not losing 100 games. Seriously. I think at this point, most Rockies fans would be happy with any kind of improvement. They have never lost 100 games in franchise history, so it would be nice if they kept that streak alive.

--Logan Burdine, Blake Street Bulletin