The Cubs have been an enigmatic team this year in a few ways. I was looking earlier for reasons to be optimistic about the Cubs, and I found some; however, the Cubs have been equally lucky in a few ways.
The Cubs are 29th in the league in Offensive Batting Average on Balls In Play, with .265. That is a historically bad number (it would be the lowest rate in the past 5 years). While there have been healthy and vigorous debates on the merits of BABIP at the individual level, there really is no argument when you consider that rate team-wide. .265 just isn't a sustainable measure, even considering the park factors that really do work to depress BABIP at Wrigley Field. I'd imagine that going forward .280 or so is a more reasonable clip (still bad, but the Cubs are a bad offensive team); that's an extra hit every 3 days, maybe, but an extra hit can be all the difference.
Unfortunately for the Cubs, they also have a Defensive BABIP of .265. It's the 2nd best rate in the league, and it's going to go up. The Cubs as a team are also 2nd in the league in GB% (50.1%), which is a primary driver of BABIP, so it's entirely reasonable to expect the Cubs to be good in this respect, but not as phenomenal as they've been (there exists a fairly loose correlation between GB% and BABIP – if only because GB isn't a line drive). Unfortunately, the Cubs are also 1st in the league in both LD% and IFFB%. Sure, these aren't stats that are necessarily going to regress; there just isn't a whole lot of room to improve in either area (the only way to go is down).
The Cubs themselves are middle of the road in nearly all batted ball categories; 17th in LD%, 16th in GB%, 12th in FB%, 25th in IFFB% (unfortunately), 7th in HR/FB. This is a) another indication of the probable improvement in BABIP and b) fairly expected given the offensive makeup of this squad. However, there is one thing that is pretty glaring, and that's the Cubs' .188 BABIP with RISP. It's 30th by a LOOONG way, and so is the accompanying .221 wOBA. In fact, I can't ever find a worse BABIP with RISP going back some 20-odd years (for that matter, I can't find a sub-.500 OPS in the fast few years, either). That change is going to come; when it does, I assure you the Cubs will look a lot, lot better.
On a related note, it appears that the Cubs are applying "selective aggression" to their plate appearances. They are 3rd in the league in swing rate (46.6%); curiously enough, they are actually still above average in P/PA (due to their ability to foul pitches off). I like the approach so far, if the Cubs can keep it up (and as an aside, I would soooo preach fouling off pitches if I was a hitting coach. I'm sure most teams do).
All told, I think most of the bounces this year have gone against the Cubs (and BP thinks so too; they have us pegged as a .500 team and I agree). The bullpen has already come around (don't look now, they are 13th in FIP). The bats will too. When they do, the wins are going to come and it's going to be deeply unsatisfying when they trade off midseason.