# Examining ISO Changes From 2009 to 2010

Every year there are several players that surprise and disappoint with their power numbers. Today, I am going to look at the players (min of 400 PA) that increased or decreased their ISO the most from 2009 to 2010. Besides just looking at the numbers, I have gone ahead and run a LOESS regression against some player’s line drive and fly ball data to help find the cause of the change in power. First of all, here are the leaders and laggards:

No real surprise with Jose Bautista leading the list. There are a couple of cases where a player went from a from one team to another and their numbers changed significantly (Jason Bay going from Boston to the New York Mets).

Next I will look to see if any of these changes were due to changes in the player’s talent or changes in their environment. To do this analysis, I am going to look at changes in the the batted ball distance and direction of fly balls (including home runs) and line drives from one year to the next. Because there are large changes from one batted ball to the next, I have plotted a LOESS curve against the data to look for small changes in the player’s hitting pattern. The distance is important to determine the power behind each hit. Looking at the angle determines if the player is able to turn on a pitch and drive it into one of the outfield corners where the fences are shorter. Now here are graphs of league’s top and bottom two players who changed their ISO from 2009 to 2010.

The data is from MLB Gameday data. The negative value for batted ball angle shows balls hit to left field and a positive value is for right field. The distance is in approximate feet. This data is not in any means perfect or close to it, but it is currently the best freely available data.

Jose Bautista (+0.184) – 2009 and 2010 with Toronto

Jose began to turn on the ball with more power at the end of 2009 and he continued that trend into 2010. His average distance hit per ball went up almost 70 feet from the beginning of 2009. To go along with a 30 degree change in angle, he became 2010’s top home run hitter. Seeing if these trends continue in 2011 will be interesting.

Adrian Beltre (+0.119) – 2009 with Seattle (Park Factor = 97), 2010 with Boston (Park Factor = 107)

Adrian’s 2009 and 2010 graphs are almost identical even though his ISO increased over one hundred points. Hitters love Fenway Park.

Jason Bay (-0.125) – 2009 with Boston (Park Factor = 107), 2010 with New York Mets (Park Factor = 95)

Jason’s distance graph is similar, but he did not turn on the ball as much in 2010. His home run numbers may go back up a little if he is able to pull the ball more. Hitters though hate leaving Fenway Park.

Ben Zobrist (-0.131) – 2009 and 2010 with Tampa Bay

Being a switch hitter, it is tough to say if the change in angle made much of a difference in Ben’s loss of power. He did drop his average distance hit by 30 feet, which explains some of his drop in ISO.

I am just beginning to scratch the surface with the batted ball data so let me know if you have any questions or if there is any other players you would like looked at (I can only go back to 2007 currently, but hope to have 2005 and 2006 data soon).

Jeff, one of the authors of the fantasy baseball guide,The Process, writes for RotoGraphs, The Hardball Times, Rotowire, Baseball America, and BaseballHQ. He has been nominated for two SABR Analytics Research Award for Contemporary Analysis and won it in 2013 in tandem with Bill Petti. He has won four FSWA Awards including on for his Mining the News series. He's won Tout Wars three times, LABR twice, and got his first NFBC Main Event win in 2021. Follow him on Twitter @jeffwzimmerman.