I just dealt with the fielding and other factors, and now I'm going to focus on the individual pitching, going from best to worst. I will ignore people that didn't pitch enough to matter.
James Russel 1.36/33/8/5
Sean Marshall 2.70/43.1/13/12
Jeff Samardsija 3.40/53/25/20
Kerry Wood 3.56/30.1/16/12
Carlos Marmol 3.80/42.2/18/18
Marcos Mateo 4.30/23/11/11
John Grabow 5.40/40/27/24
1. Many ERA's end in 0, freaky.
2. James Russel has been awesome out of the pen. His badness came in 5 starts. I guess Quade picked the wrong spot starter.
3. John Grabow is terrible.
4. The worst reliever is used more than the best reliever.
Marmol's ERA is higher because Quade never takes him out when he's in trouble (because he's the closer.) Because of that, his ERA isn't quite apples to apples to the other guys. Take away 2 bad outings totalling 11 ER and he's been awesome. Or, if he was on the visiting team, those would have been about 5-6 ER instead of 11 because the games would have been over.
So the Cubs have 3 great relievers in Marshall, Russel, and Marmol, and 2 more decent ones in Wood and Samardzija.
Going forward the pen is not a problem, however it has contributed some to the high ER total the Cubs have allowed. It's looking like most of the damage is coming from the starters.