X-factors for contenders in September (cont.)

National League

Atlanta Braves

Position: Second in NL East, 5 games behind Nationals; lead NL wild card race by 2½ games over Cardinals and 3½ games over Pirates

X-factor: Andrelton Simmons

The Braves' one lineup weakness is shortstop, where prospect Travis Pastornicky disappointed both to start the year and in a second trial in the summer. The team traded for glove man Paul Janish, who has been spectacular defensively but desperate (.197/.267/.245) with the bat. The return of Simmons, who broke his right pinky on July 8, is highly anticipated. Simmons is already one of the best defensive shortstops in the game, and his bat had been a pleasant surprise: .296/.336/.452 in 33 games. Getting Simmons back will bolster the offense and even provide a boost defensively over the excellent Janish.

Cincinnati Reds

Position: First in NL Central, 8 games ahead of Cardinals

X-factor: Drew Stubbs

After last year, we know to never say never, but the Reds are as safe a bet to set their playoff rotation as anyone. That doesn't mean they're perfect, however. They are once again struggling at the top of the lineup, with a wretched .248 OBP from the leadoff spot and a poor. 314 OBP from the second slot. Joey Votto's return will be more useful if Votto will get to bet with runners on base now and again. It's time for Stubbs, a superior defensive center fielder with great tools to play better. Stubbs has gone backwards in his age-27 season, setting career lows in everything and barely being a replacement-level player. The Reds are committed to him, and for his reputation as a manager who doesn't work well with young players, Dusty Baker has been exceptionally patient with Stubbs. Stubbs has to return that faith by becoming an asset -- a .340 OBP from here on out will be fine -- near the top of the lineup.

Los Angeles Dodgers

Position: Second in NL West, 3½ games behind Giants; 1½ games behind Cardinals for second wild card

X-factor: Chad Billingsley

Clayton Kershaw is the ace every postseason team wants to have, but behind him, the Dodgers' rotation is largely a bunch of innings guys -- yes, including Josh Beckett. Billingsley is better than that, which is why his inability to stay in the rotation this season has to be frustrating for Los Angeles. Between DL stints -- both times for pain in his pitching elbow -- Billingsley started seven games with a 1.80 ERA and a 28/11 K/BB. The Dodgers won all seven games he started. If he's done for the season -- and he may well be -- there's a huge hole in the rotation behind Kershaw. What the Dodgers can get from Billingsley, who left his most recent start on Aug. 24 early with a sore elbow and hasn't pitched since, from here on out will go a long way toward determining their fate.

Pittsburgh Pirates

Position: Third in NL Central, 9 games behind Reds; 1 game behind Cardinals for second wild card

X-factor: Jason Grilli

The Pirates' bullpen hasn't been quite as effective as Baltimore's bullpen has, but it's played a similar role in their success with just as anonymous a cast. Perhaps the best story has been Grilli, a top-five draft pick 15 years ago who, at 35, has become the most surprising shutdown reliever in the game. Grilli, who missed all of 2010 after suffering a knee injury in spring training, has bounced back to strike out an amazing 38 percent of the batters he's faced this season, with five strikeouts for every walk allowed. The Pirates have to win the close games, and having Grilli pitching the eighth inning has made them more likely to do so. With his role now critical, the Pirates need him to keep pitching as well as he has if they're to make the postseason for the first time in 20 years.

St. Louis Cardinals

Position: Second in NL Central, 8 games behind Reds; lead second wild card by 1 game over Pirates

X-factor: Jaime Garcia

With Adam Wainwright returning to his pre-surgery form, the Cardinals seem to have their No. 1 starter for the postseason. Their No. 2 is in question, for as well as both Kyle Lohse and Jake Westbrook have pitched, their pitch-to-contact style doesn't always play well against playoff lineups. Missing bats matters.

That's where Garcia, just off the DL after missing much of the season with a sore left shoulder, comes in. In two starts since coming off the DL, Garcia has 15 strikeouts and just two walks allowed. Garcia is more of a power pitcher than the other two and, at his best, is the clear No. 2 in a postseason rotation. His being a southpaw could be important as well, as the lefty-heavy Reds loom as a possible October opponent.

San Francisco Giants

Position: First in NL West, 3 ½ games ahead of Dodgers

X-factor: Brandon Belt

While the Dodgers have been acquiring every high-priced big name this side of George Clooney, the Giants have suffered the loss of their best hitter in Melky Cabrera and the disastrous month of their big trade pickup, Hunter Pence. Throw in Pablo Sandoval coming back off the DL without his bat, and the Giants' offense is sagging heading into September. That's why Belt is important.

Perceived as a disappointment for his lack of power -- four homers and a .390 SLG -- Belt is one of the Giants' most reliable sources of OBP, with a .356 mark despite inconsistent playing time. The Giants need all the baserunners they can get in a post-Melky world. Where Belt can really contribute, though, is by finding his power stroke. The fact is, low-SLG first basemen aren't helpful. Belt doesn't have to hit the longball -- a challenge for any lefty batter at AT&T Park -- but he does need to drive the ball more for extra-base hits of any kind, making up for the lost SLG that Cabrera took with him when he was suspended.

Washington Nationals

Position: First in NL East, five games ahead of Braves

X-factor: Ross Detwiler

The Nationals are the NL's Rangers, an overwhelming favorite to get into the tournament, so this is about what happens after they get there. As unfair as it is to Detwiler, he's not going to be evaluated as the effective lefty he is come October. No, he's going to be "the guy who isn't Stephen Strasburg" every time he takes the mound. The Nats' plan to shut down Strasburg means that Detwiler, their No. 5 starter, will be elevated to the postseason rotation. Himself a former first round pick, Detwiler has overcome health issues to establish himself this year, with a 3.32 ERA and an 83/36 K/BB. He's a good pitcher -- but he's not Stephen Strasburg. The Nationals will be putting a lot of pressure on him come the Division Series.