Thursday, January 20, 2011

Twins Finally Sign Carl Pavano And A Closer Look At How Luck Effects A Pitchers Peformance

After a month and change of, "they're close," the Twins and starting pitcher Carl Pavano have finally agreed on a two-year pact that will pay the pitcher 16.5m. Pavano's performance in 2010 was his best since his 2005 campaign that propelled him to a four year forty million dollar deal with the Yankees. His 4.02 FIP suggests his 3.75 ERA was a tad bit lucky, but hardly beyond the bounds of the margin of error. And now, after posting FIP marks of 4.00 and 4.02 the past two seasons it can be reasonably assured of the pitcher Pavano is today.

As I discussed extensively in this post, Pavano is essentially an innings-eating #3 at this point in his career. Thankfully for the Twins, they didn't give in to Pavano's desire for a three year deal and didn't pay the 10m+ that I thought it would take to sign him. Instead, they were able to get him for two years at an average annual value of just 8.25m.

Pavano has been worth 3.7 and 3.2 WAR the last two seasons, largely because of his ability to chew up innings in bulk. Of course, what the Twins will actually get from Pavano remains a bit of a mystery. Pavano is hardly the "ace," I've so frequently heard some fans describe him as, and 4.00 FIP pitchers have a tendency to be both good or bad from one season to the next. But he's also not a throw-away, he's somewhere in-between.

To prove that point, we need only observe his 2009 and 2010 seasons. As stated above, his FIP marks were nearly identical, yet his results - a 5.10 ERA in 2009 and a 3.75 ERA in 2010 - couldn't have been much more different. The reasons for that variation have to do with luck.

When examining pitchers, I prefer to look at their FIP precisely because it helps to remove luck from the equation and instead focuses on a pitchers performance. FIP is great not only for telling you how a pitcher truly performed, but how that performance is likely to manifest itself over time in terms of ERA. While FIP tends to be a fairly static metric with relatively small changes from one year to the next, ERA can fluctuate wildly, as was the case with Pavano.

The two primary reasons for Pavano's variation in ERA from 2009 to 2010 were his BABIP and his LOB%. On average we know that approximately 30 percent of balls in play land for hits. So when a pitchers BABIP is over or under the .300 mark, we can assume that they were varying degrees of 'lucky,' or 'unlucky.' The same is true for a pitchers left on base (LOB%) percentage. On average, pitchers will strand about 72% of baserunners and so when we observe a number above or below that mark, we can again make the 'lucky' or 'unlucky' assumption. The same is true for HR rate, but in Pavano's case, both years were essentially right on the line, so we'll avoid looking at that today.

In 2009, Pavano's BABIP was .335, about 35 points above average - meaning balls in play fell in for hits 3.5% more often than they would normally. In addition to that, he stranded just 66.1% of his baserunners, meaning that baserunners were about 6% more likely to score than normal. In 2010, both numbers flipped. His BABIP fell to just .285, about 1.5% better than normal. His strand rate was actually a tick better than average at 74%.

It's not that Pavano himself was any better or any worse from one year to the next. He was just very unlucky one year, and slightly lucky the next.

You always expect players to regress to the mean (or trend toward whatever their 'average' performance would be) and Pavano is no exception. While we have observed a wild ERA swing in just a two year period, Pavano's career shows precisely why we place value in metrics like FIP. For his career, Pavano's 4.34 ERA matches up closely with both his career FIP of 4.15 and his career xFIP of 4.11. Far more closely at least than either of his past two seasons.

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