The National League Central, which has tightened from top to bottom considerably in recent seasons, likely will continue in that direction in 2007. The bottom three teams -- the Brewers, Pirates and Cubs -- improved themselves this off season, while the top two teams, the Cardinals and Astros, appear to have taken a step back. Meanwhile, the Reds continue their metamorphosis from softball team to a pitch-and-catch club.

Only the two West divisions' clubs had smaller margins between the first and last-place clubs in 2006 than did the NL Central, which has seen its gap from top to bottom shrink from 37 1/2 games in 2004 to 33 games in 2005 to 17 1/2 games in 2006. No wonder all six teams did their best to reload this offseason -- this division is officially wide open. Since the Cubs' run in 2003, it's been all St. Louis and Houston, which finished 1-2 in all three season since then. But that run may be over.

The Cardinals lost Jeff Suppan, Jeff Weaver and Jason Marquis from their rotation and won't get Mark Mulder back until mid-season, at best. The Astros lost Andy Pettitte and Roger Clemens, at least for now and perhaps forever. Both clubs made moves to bolster their rotations, and the Astros offense should be improved with the addition of slugger Carlos Lee, but both of these perennial contenders have more questions than they've had for years.

The Reds could surprise if Alex Gonzalez and Brandon Phillips solidify the defense as expected and the pitching holds up. The Brewers signed Jeff Suppan from the Cardinals and traded for catcher Johnny Estrada to get more offense from the catching spot. They may very well have the best rotation in the Central if ace right-hander Ben Sheets is healthy.

The Cubs, of course, were the big players in this offseason's free-agent market and made a splash by bringing in CF Alfonso Soriano, LHP Ted Lilly, 2B Mark DeRosa, Marquis and OF Cliff Floyd. Unfortunately, it doesn't appear as if either Kerry Wood or Mark Prior will make significant contributions this season. If one, or both, are able to get healthy and contribute, things will get interesting.

The Pirates have been waiting patiently for their young pitching to mature and to land the left-handed power bat for the middle of their lineup. They definitely got the latter, landing 1B Adam LaRoche from Atlanta. If the young arms do indeed take a big step forward, the improved offense may finally be enough to keep them in the hunt.

It's Opening Day, it's a wide-open division -- optimism abounds for all six clubs, and rightly so. Let's take a look at the key factors and players in what could very well be baseball's most-entertaining division in 2007.

SCENARIOS

Houston Astros
They win if ...

The newcomers to the rotation can hold down the fort. It's role reversal for the Astros this season. With Lee in town to bolster the offense, the club's fate now lies with a rotation short of both Pettitte and Clemens, who may or may not return. Jason Jennings, Woody Williams and a group of youngsters will have to deliver.

Possible pitfalls
If the rotation falters and Clemens stays retired or returns elsewhere, the Astros will be in big trouble. The good news is that offense should be much improved, but this is a slim margin for error on the mound with little Minor League pitching depth ready to contribute at the Major League level.

Milwaukee Brewers
They win if ...

Sheets and shortstop J.J. Hardy stay healthy. Once again, the Brewers' hopes are pinned on Sheets. If Big Ben is healthy, and he appears to be, the improved rotation, which added Suppan, should be strong enough for the team to contend. Hardy is also key, as his defense is needed and losing him would open a hole not easily filled with Hall now patrolling center field.

Possible pitfalls
The outfield is filled with three big question marks. Hall has moved to center field, where he's never played. Geoff Jenkins or Kevin Mench, neither of who performed last year, are squabbling about splitting time in left, and Corey Hart is getting his first shot at everyday play in right. Any one or all of those situations could be problematic.

St. Louis Cardinals
They win if ...

Jason Isringhausen is healthy and can hold down the closer's role. If he falters or can't stay healthy, Adam Wainwright will have to move back to the 'pen, weakening the rebuilt rotation, which lost Suppan, Weaver and Marquis.

Possible pitfalls
This team is put together well offensively and defensively, but the rotation is a question mark even if Izzy is healthy. Wainwright and Braden Looper will get their first shots at starting on the big-league level, Kip Wells is a reclamation project and Anthony Reyes will be in his first full season in the bigs. Only Chris Carpenter is a sure thing in the rotation.

Chicago Cubs
They win if ...

The rotation -- rebuilt minus Wood and Prior -- can keep the club in games. Newcomers Lilly and Marquis will have to deliver, Rich Hill will have to prove he is the pitcher he was last September rather than the one that struggled earlier in the season and Wade Miller will have to stay healthy to round out the rotation.

Possible pitfalls
The Achilles' heel of the Cubs has been the little things, like poor defense, fundamentals and a lack of patient, productive hitters. How much of that has been solved by the offseason's free-agent splurge remains to be seen. Soriano is a fabulous multi-tool player, but will not help the club's on-base percentage or defense. DeRosa has a career .331 OBP and is not known as a glove man at second, and so on. Will the team get on base? Will it catch the ball?

Pittsburgh Pirates
They win if ...

Ian Snell and Zach Duke live up to the promise of their first two years and emerge as legitimate top-of-the-rotation starters. The offense should be better with the addition of LaRoche, but what the team really needs is a pair of top-notch starters and stability from the rest -- Tom Gorzelanny, Paul Maholm and Tony Armas.

Possible pitfalls
Last year, the Pirates offense improved when center fielder Chris Duffy returned and got on base -- with few other leadoff options, they'll need him to do it again. Also, the loss of Mike Gonzalez to add LaRoche thinned the bullpen. Salomon Torres must establish himself as a reliable everyday closer and others like Matt Capps, Josh Grabow and Damaso Marte will have to take over the setup duties.

Cincinnati Reds
They win if ...

They catch the ball. It may be just that simple. New shortstop Gonzalez should be a big upgrade and, along with second baseman Phillips, could be part of one of the NL's best double-play combinations. With Adam Dunn dedicated to improving his defense in left and Ken Griffey Jr. patrolling right instead of center field, the outfield defense should be at least marginally better as well.

Possible pitfalls
Improved defense should help what on paper appears to be a deeper pitching staff. But there is still a question as to who will close, with the club hoping that one of many options pans out. And the rotation is counting on Aaron Harang and Bronson Arroyo to repeat their stellar 2006 campaigns while getting improved efforts from Eric Milton, Kyle Lohse and whoever fills the fifth spot. Some are safe bets; none are sure bets.

IMPACT PLAYERS

Top pitcher
Clearly, the top two pitchers are Carpenter and Carlos Zambrano. Sheets, if healthy, is the dark horse. With the Cubbies likely to score a little more, let's give the nod to Zambrano this year. [Editor's note: OK, OK, Astros fans, you've been heard. If Sheets was going to be mentioned, then certainly Roy Oswalt should be part of the discussion, as well. He rightly deserves to be a part of this discussion and, along with Carpenter, should be right up there with Zambrano for best in the NL Central honors.]

MVP
Albert Pujols, no question. He may very well be the MVP of the NL, not just the division. Go ahead and pencil in 40-plus HRs and 120-plus RBIs.

NEW FACES

Carlos Lee, Astros -- Big free-agent signing will bat behind and protect Lance Berkman, giving the Astros some legitimate pop in the middle of the lineup.

Jason Jennings, Astros -- Acquired from the Rockies, he'll take the No. 2 spot in the rotation behind Roy Oswalt.

Woody Williams, Astros -- Houston native finally gets to pitch for the Astros, slotting in behind fellow newcomer Jennings in the Astros' rebuilt rotation.

Jeff Suppan, Brewers -- Former Cardinal (and Pirate), sticks in the NL Central and will bolster rotation behind Sheets and LHP Chris Capuano to give the Brew Crew a solid 1-2-3.

Johnny Estrada, Brewers -- Acquired from the Diamondbacks, he'll be the everyday catcher and should provide more punch from behind the dish.

Claudio Vargas, Brewers -- Came over along with Estrada from Arizona for LHP Doug Davis, he'll join the rotation in the five hole behind RHP Dave Bush.

Kip Wells, Cardinals -- Trying to bounce back after making just nine starts in 2006 due to injury, he'll join a rebuilt Cards rotation behind Carpenter and Wainwright.

Adam Kennedy, Cardinals -- Free agent rejoins former Angel teammate David Eckstein in St. Louis, where the two hope to reprise their stellar double-play pairing.

Alfonso Soriano, Cubs -- This offseason's marquee free agent, the Cubs will be counting on him to play an adequate CF and spark the lineup from the top with speed and power.

Ted Lilly, Cubs -- Another big free-agent signing, left-hander will be counted on to stabilize the rotation behind ace Zambrano.

Mark DeRosa, Cubs -- A third free-agent signing for Cubbies, he'll take over at second, where the club rotated players in 2006.

Cliff Floyd, Cubs -- A fourth free-agent signing, he'll get a shot to show he can play good enough defense -- and stay healthy -- to get his bat in the lineup.

Jason Marquis, Cubs -- Yet another free-agent signing, Marquis will try to bounce back from an NL-worst 16 losses in 2006.

Neal Cotts, Cubs -- Acquired from the White Sox, he'll be another piece of the Cubs' solid bullpen, but could be pressed into the rotation if necessary.

Adam LaRoche, Pirates -- The long-coveted left-handed power bat finally arrives in the Steel City, via trade from Atlanta. He'll join Freddy Sanchez and Jason Bay in a dramatically improved middle of the lineup.

Tony Armas, Pirates -- Can keep you in games when healthy. Made 30 starts last year, and Bucs would take 30 this year at the back of the rotation.

Alex Gonzalez, Reds -- A key signing for GM Wayne Krivsky, who is not-so-slowly and very surely changing the Reds from a softball team into a pitching and defense organization.

Mike Stanton, Reds -- Veteran left-hander will bolster the bullpen and likely get some opportunities to close until someone steps up and grabs the job.

ROOKIES/PROSPECTS TO WATCH

Hunter Pence, Astros -- Young CF phenom absolutely tore the cover off the ball all spring and could get a callup if Chris Burke struggles in center or shifts to second base.

Ryan Braun, Brewers -- Slugging third baseman's bat is ready for the big leagues now, but his defense is not. With no good option at third, he'll be back, and soon.

Felix Pie, Cubs -- Seemingly year-in, year-out prospect, Pie could get his chance this year, with questions throughout the OF at the big-league level.

Josh Hamilton, Reds -- The spring's best story, the real-life Roy Hobbs (albeit it much younger) has done it all -- catch, throw and man can he hit. He could very well be the Reds everyday CF if he is able to adjust when the real games start ... and if he can keep his life together.

Homer Bailey, Reds -- The best pitching prospect in the NL Central, he'll likely arrive on the big-league scene this summer and could give the Reds the boost they need if they're in it.