Roy Oswalt, Russ Ortiz, and FIP

There are a lot of different statistics out there, and it can be tough to keep up with and understand them all.  One of the ones that I've looked at quite a bit without actually understanding how it works is Fielding Independent Pitching (FIP).  It belongs to a broader class of statistics known as Defense Independent Pitching Statistics that intend to show you how effective a pitcher has really been by using only numbers that don't depend on the defensive prowess of the other 8 guys in the field.  Simply comparing FIP and ERA is usually an interesting exercise, and can give you a good piece of information when you're evaluating a pitcher. 

What's even more interesting, though, is unpacking a guy's FIP, using it as a starting point for learning about what kind of a pitcher he is.

Going into Tuesday night's game, Russ Ortiz's was sitting pretty with a very nice 3.60 ERA.  Faced with the fact that he was basically a rehab project, it's totally legitimate to wonder whether this is the result of Ortiz being good, or whether it reflects outstanding defense on the part of his teammates.  His 4.50 FIP, almost a full point higher than his actual ERA, would suggest the latter.  

Roy Oswalt unfortunately has a FIP similar to Russ Ortiz--4.41 FIP.  And yet, this theoretical FIP doesn't stray too far from his actual results--4.48 ERA. 

Most of us, before the season started, would have predicted Oswalt to have the 3.60 ERA and Ortiz to be at 4.41 or higher.  What's going on here?    

First, we need to know what goes into calculating FIP.  Here's the formula:

We need four different numbers to calculate the stat in question:  home runs, walks, strikeouts and innings pitched.  I'll list those numbers for Roy and Russ in the table that follows.  Since Roy has pitched about 40 more innings than Russ, I'm also translating Russ's stats (xRuss) to see what they'd be like if he had pitched the same number of innings as Roy.

When you compare them across the same number of innings, the first thing that stands out is that Ortiz and Oswalt have been striking out opposing batters at nearly identical rates (Roy O and xRuss have 67 and 68.4 Ks, respectively). 

The big differences between the guys are in their walks and homers.  Ortiz has been walking guys at more than twice Roy's rate.  Roy, on the other hand, has given up over 3 times the number of home runs as Ortiz.  And since home runs are weighted more than 4 times as much as walks in the FIP formula (and in real life), it's no wonder that Roy's FIP is so much higher than Russ's.

If we look to how often a flyball goes for a home run when Roy is pitching, we see that this rate is not far off from last season's performance.  12.5% this year, 12.7% last year.  What's different is that Roy is giving up a lot more flyballs than he did last year.  37.3% this year, compared to 29.2% last year.  Roy is at his lowest groundball percentage perhaps of his career.  It seems reasonable to expect that Roy will be able to get the ball on the ground more often as the season progresses, and we should then see both his ERA and his FIP settle down into normal Roy levels.  

What about Ortiz, though?  Can we expect his FIP to come down to his ERA, or should we expect his ERA to come closer to meeting his FIP?  The high number of walks but relatively low ERA seems to fit in with the idea that Ortiz lives and dies on the corners of the plat and is more of a bend-but-don't-break kind of guy.

But it's really hard to say whether his current success is predictive of future success.  His career has had so many ups and downs that it's hard to compare his current season with past ones.  In fact, looking at his pitch types (thanks, Fangraphs), he's practically re-invented himself:

He's using his fastball significantly less than at any point since 2003 (pitch type data doesn't span his whole career).  Conversely, his curveball makes up almost a full fifth of his repertoire, which is significantly more than at any point in his career.  Because of this major shift in his pitch selection, it seems really difficult to make predictions for Ortiz based on his pre-surgery career. 

Whatever he's doing, let's keep our fingers crossed that he's able to keep on doing it.