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Is Ortiz Powering Back Up?

David Ortiz had a horrible start to the season, going the first month and a half (154 PAs) without a home run. But recently he has turned it around, hitting five home runs since June 6th. Does this mean that Ortiz’s power is back, or has the recent HR outburst been a small sample size fluke build on a couple lucky shots?

One way we can answer this question is head over to Greg Rybarczyk’s Hit Tracker and see if his HRs were lucky or not. This shows Ortiz tied for the league lead with three lucky HRs, not encouraging. Greg’s information is great (providing the most accurate data available on every aspect of HRs we could ask for), but it only provide data about Ortiz’s HRs and there is another half to luck, maybe Ortiz has hit a number of long fly balls that just barely didn’t go for HRs.

I wanted to see a complete picture of Ortiz’s power including all of his fly balls, so I needed to look elsewhere for the distance on his non-HR fly balls. Back on June 5th when Ortiz was seemingly still in his slump John Dewan presented the average distance of Ortiz’s balls in the air using the Baseball Info Solution (BIS) data. It showed a serious drop in his average distance compared to 2007 and 2008. Unfortunately the BIS data are not publicly available so I could not use them to look at his fly balls during his recent power surge.

Batted ball location data are publicly available through MLB’s Gameday. They report the location x and y coordinate of every batted ball in pixel units, which are displayed on the field images in the MLB Gameday application and then stored in XML format. Peter Jensen came up with translation factors to convert Gameday provided pixels to feet for each ball park. Unfortunately Jensen found that the conversion factors change year to year and you need a whole year of data to come up to determine the factors. So I am going to have to use Jensen’s 2008 conversion factors to look at Ortiz’s fly ball distances and hope that we are not that far off. Luckily I can use Dewan’s BIS data to see how close they are.

 David Ortiz ball in air average distance (feet)
+------------------+---------------+---------------+
| Year             |     BIS Dist. | Gameday Dist. | 
+------------------+---------------+---------------+
| 2007             |           290 |           291 |
| 2008             |           273 |           279 |
| 2009 pre-June 5  |           254 |           256 |
| 2009 post-June 5 |            NA |           300 |
+------------------+---------------+---------------+

For 2007 and 2008 I used the appropriate conversion factors from Jensen and the BIS and Gameday average distances are surprisingly close. It is really an endorsement of the quality of data from both BIS and Gameday, and Jensen’s conversion factors. For 2009 I had to used the 2008 factors on the 2009 data, and luckily the BIS and Gameday numbers came out very close. So I am fairly confident going forward with the 2008 conversion factors on the 2009 data.

If you trust the 2008 conversion factors on the 2009 data, over the past two weeks Ortiz’s balls in the air have averaged 300 ft, higher than in 2007 and 2008. That looks good.

Here are the distances of all of his balls in the air by date with the home runs filled in. The straight line is his average 2008 distance and the wavy line a smoothed rolling average of his 2009 distance.

dist_fig

You can see he started out a good 20 ft below his 2008 average, but starting around the end of May his average distance has raised steadily. This graph also shows that in the past couple weeks in addition to his six homers he has had a number of other long fly balls. This is a small sample, but things look qualitatively different for Ortiz since the end of May, an encouraging sign for him and the Red Sox.