Collection of rumors and surmizations: Soriano gone, Zambrano stay, Pena replaced by Anthony Rizzo, Garza likely to be traded. Soto is a maybe, but I think not after his down year. Samardzija to become a starter. Sean Marshall might get traded. Byrd gone. These people rumored to get traded might not happen until mid season.
In the bank: Ian Stewart replacing Aramis Ramirez. David Dejesus in to play RF.
At this point, the best guess at the outfield picture is Tony Campana in center, DeJesus and Byrd in right and left. That would be a tremendous defensive outfield, and an OK hitting one. Tony Campana saved 10 runs in about 30 games worth of fielding according to UZR.
With Ian Steward replacing Ramirez and Castro improving the infield defense will also be a strength. Rizzo is also an excellent defender, as is Darwin Barney. This is once again a just ok group of hitters. Platooning Baker in against lefties will help. Dewitt might periodically spell Barney vs righties also.
I think this would be one of the best fielding teams around if they decide to stick with Campana. Defense goes farther than people realize. It has a trickle down effect of helping pitchers play better than they really are.
In the bullpen Kerry Wood and Carlos Marmol are quite effective. Marcus Mateo also has promise. James Russel and Marshall (if he stays) are great from the left side. There are a few other names in contention that might be surprise contributors. Grabow is gone!!!!
Starters (highly up in the air right now) looking like Andrew Cashner, Jeff Samardzija, Ryan Dempster, Carlos Zambrano, Randy Wells. It looks like a list of losers honestly, but I really have high hopes for all these people to varying degrees, with the biggest breakout surprise going to Samardzija. Dempster and even Zambrano are solid bounce back candidates. I could see this staff having an ERA below 3.90 with a shot to be much better.
The Cubs GM has suggested he doesn't want to take away the chance of a surprise contention. For this reason I think most of the trade pieces will go mid season instead of this off season. The most likely exception is Garza, as I believe the Blue Jays really want him.