Consistency Factor

Hey everyone, I'm a regular poster at the Mets SB Nation site, Amazin Avenue.  I put this little case study together and thought you guys might be interested since there's some pretty interesting info in here; basically I developed a stat that I feel is pretty useful. So enjoy.

In honor of Oliver Perez week, I figured I would try to wrap up this case study on consistency.  For anybody who missed it, I took a shot at quantifying start to start consistency, or what I'm calling Consistency Factor (CONF), for pitchers a few weeks back in this post.  It was enlightening but the results just didn't seem quite right.  So I've made some tweaks, basically utilizing Bill James' Game Score to evaluate each game started instead of WPA.

A brief refresher for those who missed the original post or forgot how it worked:  Basically I evaluated a pitcher's starts individually (using Game Score) and then took a Standard Deviation of those 30-something starts.  The higher that #, the higher the range a pitcher regularly pitches within thus the lower his consistency.  So lower = better.  However, this # does NOT relate to how effective a pitcher is.  A pitcher can have the worst CONF but still be very good, all it means is that he doesn't pitch consistently from start to start.

I compiled the CONF #'s from 2008 as well as the last 3 seasons totaled for every qualifying NL starter.  However, before we dive into all of those #'s, here's a nice visual breakdown of this idea using, who else, Oliver Perez:

So as you can see, each point represents a start measured in Gamescore (high=good low=bad), the gray area represents 1 Standard Deviation away (in both directions) from Oliver's Mean (which happened to be a Gamescore of 51.65).  In english, the blue points are each start, the gray represents the average range where he usually pitches and the red baseline is the level of his average start in 2008.

Now let's take a look at another pitcher for some perspective.  How about Tim Lincecum:

First of all, Lincecum's Mean or average start is obviously higher (Gamescore: 62.06), the guy did win the Cy Young.  (For reference, a Gamescore of about 50 represents Replacement Level)  More importantly for us, Lincecum's starts are packed much more densely within his average range than Oliver's.  Only a handful of starts fall outside of the gray area whereas Perez has many more fall outside.  As a result, Lincecum's Average Range is smaller, which represents less variation and higher consistency.

As far as the most important figure that we can draw from these graphs, its that Standard Deviation I mentioned that makes up the gray Average Range.  This is the figure that represents Consistency Factor.  For Lincecum it's 13.18.  For Perez, it's 17.08.  The league average is around 16.

So now that we can kind of visualize where these #'s come from, lets look at the results.  I grouped all NL starters (who pitched at least half a season in '08) by team and I've got all the teams here so lets look at them by division, East first of course:

Well there are a few interesting things we can see here:

• We already knew that Johan was awesome, now we know hes consistently awesome.
• Apparently Maine & Redding are very consistent as well, although Perez, Livan & Pelfrey are not.
• However, Oliver Perez: not that inconsistent... at least not as much as many of us would think.
• Brett Myers on the other hand... ugh.
• However, Cole's about average and guy's like Moyer & Blanton are really only valuable because of their consistency.
• And damn, we all know Josh Johnson is going to be great but hes already pretty damn good (though to be fair this was based on only half a season of starts).
• Another surprise, Daniel Cabrera wasn't bad at all in '08.

Onto the NL Central:

• The Cubs have a remarkably consistent staff...
• ...except for Carlos Zambrano who is officially THE least consistent starter in the NL.
• Surprisingly consistent seasons from the 2 young Reds rookies especially Volquez, not so much from their 2 vets though.
• As usual Paul Maholm is quietly very good.
• And a shockingly consistent season by Todd Wellemeyer and that came in only his first season in the rotation.

And finally the NL West:

• 2 more young guys with surprisingly consistent seasons in LA, not so much for Hiroki Kuroda.
• What's the only difference between the Giants rotation and a roulette wheel? Tim Lincecum.
• SI product Jason Marquis, very nice.
• Surprisingly high from Webb, even more from Garland who is known for his consistency.
• And a perfect example of what I said earlier about consistency not always equaling performance, Kevin Correia the NL's most consistent crappy pitcher (Gamescore Mean: 43.63...ugh); looking at these #'s, it's amazing he is still in a Major League rotation today.

And last but not least, here are the rankings of the best and worst performers of 2008:

• Redding on the Top 5 (3 Year) list, I didn't expect that
• And John Garland on the Bottom 5 (3 Year) list, I bet people would have had him pegged as super consistent not the other way around...
• Another supposed "Mr. Consistency", Derek Lowe finds himself on the Bottom 5 (3 Year) list
• And yes, Oliver would have been on that list too but I gave him a little home-cooking if you will by excluding that bizarre stretch in '06; basically I'm just evaluating him in his time with the Mets.

So I hope this has been enlightening.  At the very least I figured it would break up the interminable dross that we've witnessed in the FanPosts recently.  Just as last time, I apologize for the high level mathematics and such but thats the breaks.

I set out to disprove the myth of Oliver Perez as "Mr. Inconsistency" and I think I've done that.  That title definitely goes to Carlos Zambrano.  Perez is definitely on the higher end but even if I included all of the #'s, he's not as bad as the media portrays.  I think a lot of that mindset derives from how he can be so inconsistent in-game or inning to inning rather than game to game, which definitely is no myth.  That would be another interesting case study but thats another story for another day.  As far as what this means to his overall performance, not too much because he's obviously been terrible this year anyway.  But at least he's been consistently terrible...

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