A couple of months ago, I (and others) noted that Marquis was doing it with smoke and mirrors. Despite a hot streak and a sub-2.00 ERA, his strikeout rate was terrible, and against the laws of God and nature, he wasn't giving up any home runs. I predicted then that Marquis would soon come crashing down to Earth, and that he has. Since I wrote those words on May 10th, Marquis has gone 1-4, and has seen his ERA rise from 1.70 to 4.03. He's sporting a 6.12 ERA for June and July (allowing eight unearned runs in that time as well), and has began to give up home runs at a Marquisesque pace once again.
Meanwhile, Carlos Zambrano has gotten his mojo back, lowering his ERA by more than two runs since the beginning of May during which time he has gone 9-5. Despite early worries that he was hurt, Zambrano is going longer and longer into games as the summer wears on, and his strikeout rate has improved as well. Basically, he's Carlos Zambrano again.
What does that tell us? Mostly that the mean is a powerful master which demands fealty in the form of regression to its mighty side. It also means that the Cubs may very well have cost themselves a lot of damn money by not signing Zambrano to a $72 million extension when they had the chance back in April.