According to Paul Maholm, the next person to join the pitching staff of the 2012 Cubs is… Paul Maholm.

In an unorthodox move last night, Maholm announced his signing by tweeting “Just wanna say thank u to everyone that has cheered for me during my career as a Pirate. I loved my last six plus years in the city. I hope to get to continue some things when I visit during the year and start some great things as I start my Cubs career. #GodBless. Looking forward to seeing the fans at Cubs convention this weekend and getting to know all the guys. It's gonna be fun.”

Maholm will receive a one year contract worth $4.25 million, with an attached team option for 2013 at $6.5 million with a 500k buyout. He’ll join a rotation that is likely set to feature Ryan Dempster, Randy Wells, and fellow newcomers Travis Wood and Chris Volstad. This move is certainly a precursor for something, as the Cubs will have to make space on their 40 man roster to accommodate the signing. It is widely expected that the corresponding move will be the trade of Matt Garza, which should occur somewhat soon.

I anticipate a more than a few fans and media personalities will be critical of the move. After all, Matt Garza was the Cubs ace in 2012. How can you replace a man like that with a schmuck who has a career 53-73 record with a 4.36 ERA? Well, you don’t. Paul Maholm wasn’t brought in to be Matt Garza. He was brought in to be Paul Maholm. And to write him off as a schmuck (seriously, what kind of goon uses that word?) is to do him a great disservice.

Maholm has quietly been a very consistent pitcher the last five years… if you can ignore all the inconsistency. Perhaps I should explain that better?

On the surface, Maholm’s performance seems to jump all over the place. His ERA the last five years has gone from 5.02 to 3.71 to 4.44 to 5.10 to 3.66. That’s a minimum move of two thirds of a point of ERA per year in a seemingly random direction (and an average move of a little more than a point). El Duque’s arm slot was less random than that. But if you look underneath the hood you’ll see that Maholm hasn’t been as inconsistent as you’d expect.

(The following table is stolen from fangraphs, as I cannot code tables into this blog due to a preponderance of stupidity)

His K/9 (strikeouts per nine innings) has been remarkably consistent over his career, typically floating around the 5.5 mark. Likewise, after making some adjustments following his first full season in the bigs, his BB/9 (walks per nine innings) has sat around 2.75 with very little movement. He also seems to have made adjustments to limit home runs, posting nearly identical HR/FB rates in each of the last three seasons. All this paints a picture of a pitcher who relies quite heavily on his defense.

If you haven’t figured out where I’m going with this already, I’ll get straight to the point. The inconsistency in the ERA of Paul Maholm isn’t caused by anything Paul Maholm can control. Once the ball comes off the bat, what happens is determined solely by the defense and sheer luck. In the last half decade with the Pirates, both have been rather volatile when Maholm is on the mound.

Maholm is an extreme groundball pitcher. His performance is primarily defined by how well the infield behind him performs. According to Total Zone, in the timeframe from 2007 to 2011 the Pirates infield defense has combined for totals of -14 runs, + 4 runs, -12 runs, a staggering -49 runs, and -5 runs. Those numbers exclude catcher defense, which is somewhat difficult to quantify. Still, you’re probably noticing that Maholm’s ERA is lowest in the seasons where the Pirates infield defense was closest to league average. Also, when the defense sucked, so did Maholm.

So what can Cubs fans expect from Paul Maholm? He won’t strike many batters out, but he doesn’t hurt himself much with free passes or the long ball. You can expect to see a TON of groundballs. The Cubs infield defense isn’t great, but Stewart and Barney are both above average. LaHair is a relative unknown. So ultimately, as is true for most Cubs fans lately… everything revolves around Starlin Castro. If he makes continued defensive improvements we could be in line to see Maholm’s best season ever. If he stagnates, Maholm should remain a league average pitcher and steady #4 starter. That’s an extremely valuable asset to have on a club that got 44 starts from Casey Coleman, Rodrigo Lopez, Ramon Ortiz, and Doug Davis last year.