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Boston Red Sox DH David Ortiz: The Fear of Selling Low

David Ortiz's power slump to begin the 2009 season has caused much of the baseball world to try and explain why is has occurred.  Baseball Prospectus sends its Three-Headed Knight to battle while Crooked Pitch focuses on pop-ups by Big Papi.

My focus is more about the fear of dealing David Ortiz at his low and seeing him rebound to have an acceptably good power season. (After last season, visions of 2006 no long dance in my head.)  But how can one even conceptualize this all-too-common monkey wrench that prevents many fantasy baseball trades?

The key was trying to focus on what happens immediately after a trade. After all, the fear of selling too soon is really the fear that the player will immediately rebound to your expected levels of production. I decided the first ten games after trading a player was a short enough time to have trader's remorse linger, but also long enough for the player(s) acquired to enough accumulate stats to lessen the trader's remorse.

Using Baseball Musing's Day by Day Database, I was able to get David Ortiz's game-by-game efforts for his career. Once this was done, looking at 10-game periods was easy enough.

A look at Ortiz's career as a homerun hitter over rolling ten-game periods gave me some consolation as the vast majority of his ten-game periods did not begin with a HR especially in the last two seasons since he peaked with 54 HRs in 2006. Even then, two out of every three rolling periods did not start with a HR.

As a matter of fact, those last two seasons saw a big jump in the total number of ten-game periods where he did not homer at all. From 2004-2006, Ortiz went ten games without hitting a HR a total of five times covering 433 periods (1.12%). In 2007 and 2008, that has leapt to 15 and 17 times, respectively, (13.3%).

Even more soothing, is the decrease in the frequency that Ortiz would hit four, five or six+ HRs in any ten-game period. After slugging at least four HRs in that period 31.6% of the time in 2005 and 48.9% in 2006, Ortiz did it in only 20.7% of the periods in 2007 and just 13.8% in 2008.

None of these numbers says Ortiz won't hit HRs in 2009 despite not having any in the 22 10-game periods so far, but the data certainly suggests that the hey days of 2005 and 2006 are gone. I'll leave the assigment of blame for that disappearance to others.

Rolling Ten Game Periods:

Year 0 HR 1 HR 2 HR 3 HR 4 HR 5 HR 6+ HR % Period start 0 HR
2008 17 23 16 31 9 5 0 0.832
2007 15 26 45 25 16 13 0 0.807
2006 2 6 26 40 27 26 15 0.676
2005 2 20 41 41 20 14 12 0.753
2004 1 19 41 54 12 7 7 0.738
2003 16 40 18 9 11 11 14 0.815
2002 36 34 24 12 1 3 6 0.853