from Amazon
Wednesday, July 26, 2006
Mark Teahen, and GB/FB ratios
According to FanGraphs, Mark Teahen had a GB/FB ratio of 2.22 in 2005, and 1.37 in 2006. Quite a shift, wouldn’t you say? In 2005, 53% of his contacted balls were groundballs, while in 2006, it’s 50%. Quite similar, wouldn’t you say? What’s the difference?
The difference is that Line Drives are not calculated as either GB or FB. His entire shift is in his LD to FB ratio, from 1.00 to 0.27. Now, that’s quite a shift.
Personally, I prefer that if you are going to go with just one ratio, then use the GB to Airball ratio. However, I hate ratios, because of their non-symmetry. If the league average GB to AIR ratio is 1, then a 1:2 ratio is symmetrical to 2:1 ratio. However, 1:2 is 0.50, and 2:1 is 2.00. So, why not do the most simple thing, and quote the guy’s GB percentage. In this case, Teahen went from 53% to 50%. His Airball percentage is obviously 47% last year and 50% this year.
Just looking at his chart, I’m guessing that the shift in LD to FB means that he’s hitting the ball with more loft. That’s further evidenced by his HR/FB rate doubling from 2005 to 2006. Is this statistical significant?
Teahen has 24 LD and 65 FB, whereas last year he was 50/50. It’s highly unlikely that the 50/50 was anything close to his true split. I doubt any player has that kind of split. Either it was a blip, or the Royals scorekeeping was off with him. More interesting is his HR/FB rate doubling. One standard deviation of HR, given 65 GB is .04 HR/FB. Teahen’s HR/FB changed by .08 HR/FB (and that’s from one small sample to another small sample). In and of itself, it’s not very significant.
However, if the LD to FB ratio change is something real, if he is in fact hitting the ball with more loft and distance, then this change is more real. That is, while we expect our player’s sample HR/FB to regress to the league mean of around 10%, if we know something more about this hitter, for example, the % of FB that are long flyballs, then we would have a higher mean to regress to.
It’s cases like these that having a good scout would be invaluable.