What once looked like a division that the Chicago Cubs could take easily has instead turned into the most competitive division in baseball, as the National League Central boasts three of the top teams in the league fighting for just two playoff spots. The Milwaukee Brewers were patching up their early-season issues even before acquiring ace C.C. Sabathia from the Indians, and the St. Louis Cardinals have surprised many analysts by hanging on this far, powered by the best lineup in the NL. Now, with less than a month and a half of games to go and just eight games separating these three in the Central as of press time, it’s time to wonder who will come out on top.

The Cubs remain the best of the bunch, at least if you’re looking at their expected records. Thanks to a run differential of +170 — far and away the best mark in the majors — the Cubs are actually two wins behind the pace they should be on, with 77 victories on the season. A balanced attack is what’s behind the Cubs’ success, as they can hit, pitch, and field with the best of them. Offensively, their team Equivalent Average (EqA) of .274 is second in the NL and third in the majors; they have also scored far and away the most runs in the NL, and sport an impressive team line of .280 AVG/.358 OBA/.446 SLG. Despite extended slumps from key contributors from earlier in the year — such as Kosuke Fukudome, hitting just .208/.284/.306 since July 1 — the Cubs’ lineup has continued to chug along, and they have even closed the gap between their home and road performances offensively.

The Cubs’ pitching is just as potent. They rank first in the majors in Support Neutral Lineup-adjusted Value Above Replacement (SNLVAR), and that’s with just seven starts out of Rich Harden, one of the top starters in today’s game (as long as he’s healthy enough to pitch). Beyond Harden, the rotation boasts Ryan Dempster (5.5 SNLVAR, fifth in the NL) and Carlos Zambrano (4.6, 11th). Via Defensive Efficiency, their defense rates as the NL’s best and is tied with the Tampa Bay Rays for the best in the majors. Defensive Efficiency measures defensive success based on the percentage of balls in play converted into outs, a more accurate measure of fielding prowess than fielding percentage, which simply looks at balls that are fielded. When you combine the Cubs’ fielders converting the highest rate of balls into outs with the fact that their pitchers lead the majors in strikeouts, you can see why the staff is cruising.

The Brewers would be in a better spot if they had not underachieved for the first two months of the season. But as it is, they are the favorites for the wild card in the NL. At the end of May, the Brew Crew’s record stood at 28-28, and they were in fourth place in a crowded NL Central, seven games back of the Cubs. Their run differential of -23 did not bode well for their future performance. But a solid June threw them right back into the thick of things: They went 16-10. The club then addressed their biggest need — help in the rotation — by adding last year’s American League Cy Young winner, Sabathia. Since his first start on July 8, the Brewers have gone 24-15, and their season run differential has improved to a solid +52. If they had been playing this well all season, they would be right with the Cubs atop the division, rather than five games back.

One of the major reasons for the team’s rebound from last year’s disappointing campaign has been the improvement of the defense. In 2007, the team’s defense was a serious issue that hurt the pitching staff; they ranked 13th in the NL in Defensive Efficiency, converting just 68% of balls in play into outs. This year sees the Brewers rank third in the league, converting nearly 71% of balls in play into outs, a massive increase that has helped out their pitching dramatically. With that kind of assist, the Brewers’ pitching ranks second only to the Cubs in team SNLVAR. Unlike the Cubs, though, the Brewers rely on their starting pitching to win, as it is their strongest point; though solid, the lineup is not much better than average, with a team EqA of .264 (.260 is average). The bullpen, while an improvement over last year’s pre-Francisco Cordero disaster squad, is ranked sixth in the NL and lacks the dominating presence or depth of some of the more productive pens — it’s Salomon Torres or bust.

As for the Cardinals, they sit 21/2 games behind the Brewers for the wild card and have enough of their own strengths to stay in this race until the end. St. Louis has the top offense in the NL, as their .276 team EqA is just a sliver ahead of the rival Cubs, but they have weaknesses in other areas. Their bullpen is the most obvious example, ranking 13th in the NL in WXRL. Losing former closer Jason Isringhausen to injury may be a positive for the beleaguered unit: With -2.325 WXRL, he was easily the least productive member of the pen and the main reason why they do not rank with the Brewers in terms of overall effectiveness.

Thankfully for the Cardinals, their rotation is in much better shape, ranking sixth in the NL in SNLVAR and boasting some solid options of their own. Surprise seasons from Todd Wellemeyer (4.2 SNLVAR) and Kyle Lohse (4.3) have kept them in the race, and with Adam Wainwright heading back to the rotation, they should have the horses to run with the Cubs and Brewers.

That said, the bullpen issues in St. Louis loom large in what should be a tightly contested division. It’s the one weakness in a key unit among the three teams that could be described as glaring and is the sort of thing that can ruin the playoff hopes of a team already playing catch-up. However, given the quality of the Cardinals lineup and the fact that they do have a solid rotation, a hot stretch could be all the team needs to vault their way into an October appearance, ahead of at least one of their more well-rounded adversaries.

Mr. Normandin is a writer for Baseball Prospectus. For more state-of-the-art commentary, visit baseballprospectus.com.