New York Yankees
Position: First in AL East by 2 ½ games
X-Factor: Bartolo Colon
The Yankees can expect to get great starting pitching from CC Sabathia, who will open the Division Series for them and pitch as often as possible. The dropoff from Sabathia is significant, however, and the best of the remaining starters -- the likely Game 2 man -- is Colon. In his comeback season after missing all of 2010, Colon has been nearly as good as he was in his Cy Young season of 2005, striking out 123 men and walking just 32 unintentionally in his 145 innings. He hasn't been quite as effective since injuring his left hamstring in June: a 4.46 ERA and 51/17 K/BB, with a whopping 10 homers allowed in 66 2/3 innings over 12 starts. The Yankees have a deep bullpen that can carry the rotation to some extent, but the compressed postseason schedule means that they will have to get some kind of run prevention, and innings, from the non-Sabathia starters. Colon, with his demonstrated command, is their best chance for quality postseason starts.
Boston Red Sox
Position: Second in AL East; wild card leader by 7 games
X-Factor: Dan Wheeler
The Red Sox are set at the back end of the bullpen with Jonathan Papelbon having one of his best years in the closer role, and Daniel Bard setting him up -- Wednesday night's 36-pitch disaster notwithstanding. There is a gap between the rotation and those two guys, and while Josh Beckett and Jon Lester often cover that themselves, any game in which they don't -- or that's started by John Lackey or Erik Bedard -- reveals a potential problem. Wheeler, who has been part of successful postseason bullpens in Houston and Tampa Bay, could be part of the solution. Since a wretched opening month and a trip to the DL with a calf injury -- or perhaps just a bruised ERA -- Wheeler has a 2.54 ERA and a 31/6 K/UIBB ratio. With Alfredo Aceves more of a long man, the Red Sox need a third reliable arm in their playoff bullpen to get important outs in the sixth and seventh and get them to Bard and Papelbon. Wheeler is most qualified for the role.
Position: First in AL Central by 9 games
X-Factor: Austin Jackson
The centerfielder's importance to the Tigers has been revealed over the past month, as his torrid pace (he's hitting .400 over his past 10 games) has fueled an offensive surge that has helped Detroit all but lock up the AL Central. The Tigers have a front-loaded roster, with stars Justin Verlander, Miguel Cabrera, Alex Avila and Jhonny Peralta providing most of the team's production this year. Jackson, who started the year poorly, has re-established himself as the leadoff man, something a team with the Tigers' terrific middle of the order needs to maximize run scoring. As Jackson goes, so goes the Tigers' offense.
Position: First in AL West by 2 ½ games
X-Factor: David Murphy
With Nelson Cruz on the DL with a hamstring injury, Murphy has gotten his best opportunity to play this season and he's shown well, batting a torrid .467 in September with an .833 slugging average. If Murphy hits, it allows manager Ron Washington a lot of additional flexibility without sacrificing performance, as Murphy can play centerfield as well as right. He helps balance a Rangers' lineup that lists a bit to the right side, and he gives Washington the option of DHing Cruz or even platooning him to take some of the pressure off the healing hammy. On any given day Murphy could be one of just three lefties in the Rangers' lineup; they need him to be a productive one.
Los Angeles Angels
Position: Second in AL West by 2 ½ games
X-Factor: Bobby Abreu
The Angels are built on their rotation, with two No. 1 starters in Dan Haren and Jered Weaver and a legitimate No. 2 in Ervin Santana. What they don't do well is score runs, particularly against right-handers -- just two AL teams, bottom-feeders the Twins and Mariners, perform worse against righties. Abreu, who bats third against righties, is the team's hope against them, one of just two Angels starters with a good OBP against RHPs -- .369 for a team that regularly plays seven guys below .330. If the Angels overtake the Rangers, they'll need Abreu to hit, particularly if they play the righty-heavy Yankee staff.
Position: First in NL East by 10 ½ games
X-Factor: Jimmy Rollins
One reason the Phillies have the best record in baseball is the comeback of Rollins, who has 14 home runs and 28 stolen bases as part of his best year since 2008 after two poor, injury-plagued campaigns. The Phillies do not have a credible backup, and having to bat Shane Victorino leadoff is a waste of Victorino's power from both sides of the plate. Rollins is also a superior defender to the available options, no small consideration for a team whose pitchers have one of the highest groundball rates (47 percent) in baseball. He's an asset on defense and a key part of the offense, the guy who Chase Utley and Ryan Howard drive in.
Position: Second in NL East; wild card leader by 6 ½ games
X-Factor: Martin Prado
Maybe the most consistent hitter in baseball the past three seasons, Prado is having his worst year, down to .260 with a terrible .307 OBP. Unlike with Jason Heyward, whom manager Fredi Gonzalez has benched for not hitting, Prado continues to bat second for the Braves. This is a problem if he doesn't hit -- not only is his low OBP crippling the offense in the most important spot in the order, but as a right-handed groundball hitter, he's a huge double-play threat. Prado is fourth in MLB (min. 200 PA) in double-play rate, grounding into one every four chances he has. The Braves need the line-drive Prado back, or their already shaky offense could fall off the cliff.
Position: First in NL Central by 8 ½ games
X-Factor: Casey McGehee
Protection is an overrated concept in most cases. Hitters hit what they hit regardless of who's batting behind them, with the only change being to walk and intentional walk rates. If the gap between two hitters is large enough, though, it can neuter the first's ability to produce. In the absence of Rickie Weeks -- who may be back this week and who is key to the Brewers' hopes -- it falls to McGehee to protect Prince Fielder, and he's not up to the task. McGehee has both an OBP and a SLG more than 100 points lower than Fielder's. Since Weeks went on the DL, Fielder has walked in one of every seven PA, and has drawn 12 intentional walks in 39 games. McGehee, who was productive in 2009 and 2010 before collapsing to .236/.293/.360 this year, has to hit enough to dissuade teams from turning him into the escape hatch for any Brewers rally.
Position: First in NL West by 7 games
X-Factor: Joe Paterson
The rookie lefthanded one-out guy (LOOGY) has had a strong season after being selected in the Rule 5 draft, holding lefties to a .216 BA while striking out more than 20 percent of the ones he's faced. Whether the D-backs catch the Phillies or the Braves in the first round, they'll be seeing a team with left-handed power, putting the onus on Paterson to get out Utley, Howard, Heyward (if he's ever found) and Brian McCann late in postseason games. While the Snakes could go with Zach Duke or Alberto Castillo as a second left-hander, it will be Paterson who gets used in the biggest spots against the best players. Their advancement could come down to how he pitches in high-leverage situations.
San Francisco Giants
Position: Second in NL West by 7 games
X-Factor: Aubrey Huff
My editor made me do this. The Giants are seven games back with a tragic number of 13 and just three head-to-head matchups with Arizona remaining. They probably don't belong in any serious discussion of playoff contenders. Yet San Francisco still has a tremendous pitching staff, so if a miracle happens and the Giants do get to October, it will be up to one of the biggest reasons they're seven games out -- Huff -- to help them advance. The Giants have a bad offense, without nearly enough OBP, and when he's at his best Huff gets on base and hits for power. The Giants seem determined to not play Brandon Belt -- their best first baseman and third-best hitter -- so it's up to Huff to give the team a third middle-of-the-order threat to go with Pablo Sandoval and Carlos Beltran to support that great pitching staff.