I was over at TigsTown recently and they were discussing which Tigers minor leaguers were best at "hitting for average". They judged the players based on
scouting and on
statistics. From the scouting perspective, they considered qualities such as consistently making solid contact, hitting all different kinds of pitchers and using the whole field. Statistically, they used use items such as batting average, percent of plate appearances that resulted in the batter making contact, batting average on balls in play and strikeouts per at bat. It's premium content so I can not reveal many of the results but I'll mention that second baseman Justin Henry fared well on the hitting for average skill on both scouting tools and statistics.
What I wanted to do here is rate the major league Tigers on hitting for average in 2008. I'm not a scout so I just considered statistics and not tools. Since there are more statistics available for major league players, I used a different algorithm than the one used at TigsTown. I started by looking at batting average. The Tigers 2008 batting averages can be found in Table 1.
Table 1: Tigers Batting Averages in 2008 player | avg |
Magglio Ordonez | .317 |
Placido Polanco | .307 |
Miguel Cabrera | .292 |
Carlos Guillen | .286 |
Curtis Granderson | .280 |
Edgar Renteria | .270 |
Marcus Thames | .241 |
Gary Sheffield | .225 |
Brandon Inge | .205 |
The problem with batting average is that what happens after the batter hits the ball is largely out of his control. He can hit line drives that are caught or soft bloopers that escape the grasp of infielders. Often times, these fortunes and misfortunes even out throughout the course of a season but sometimes they don't. Thus, a player's batting average is not repeatable. That is, it varies a lot from
season to season (correlation =.43).
A statistic which is much more repeatable than batting average is contact percentage (correlation = .90). Contact% is the percent of balls that a batter swings at which result in the batter making contact. This stat was abstracted from
Fan Graphs which has fast developed into one of my favorite sites on the internet. Another contact hitting statistic is strikeouts per at bat which has a year to year correlation of .80. I could have used K/PA instead but the Fan Graphs database doesn't have all the items needed to calculate plate appearances and merging with my other database would have been more trouble than it worth right now. The Tigers leaders on contact% and K/AB are presented in Tables 2 and 3 below.
Tables 2: Contact percentage for Tigers in 2008 player | contact % |
Placido Polanco | .927 |
Carlos Guillen | .862 |
Edgar Renteria | .856 |
Magglio Ordonez | .851 |
Gary Sheffield | .830 |
Curtis Granderson | .796 |
Miguel Cabrera | .775 |
Brandon Inge | .758 |
Marcus Thames | .743 |
Table 3: Strikeouts per at bat for Tigers in 2008 player | K/AB |
Placido Polanco | .074 |
Edgar Renteria | .127 |
Magglio Ordonez | .135 |
Carlos Guillen | .160 |
Gary Sheffield | .199 |
Curtis Granderson | .201 |
Miguel Cabrera | .205 |
Brandon Inge | .271 |
Marcus Thames | .301 |
It probably comes to no surprise that Placido Polanco led the Tigers in both categories. In fact, he led the American League in both. Contact% and K/AB give us information about ability to make contact but they tell us nothing about how solid the contact was. Line drive percentage helps us there. You can often tell about a batter's fortunes by looking at line drive percentage. A player with a high line drive percentage relative to his batting average is possibly hitting into a lot of hard outs. Conversely, a batter who has a low line drive rate relative to his batting average is possibly getting a lot of cheap hits. The Tigers line drive percentages are listed in Table 4.
Table 4: Line drive percentages for Tigers in 2008 player | line drive % |
Edgar Renteria | .222 |
Magglio Ordonez | .204 |
Carlos Guillen | .202 |
Miguel Cabrera | .196 |
Curtis Granderson | .191 |
Placido Polanco | .187 |
Marcus Thames | .170 |
Brandon Inge | .164 |
Gary Sheffield | .143 |
It's a little surprising to see Edgar Renteria's high line drive rate. This suggests that he may have been unlucky and that his batting average rebound might rebound in 2009.
I combined the above four items to arrive at one statistic which describes the hitting for average skill. First, I normalized each number, so that they all had the same scale - an average of 0 and a standard deviation of 1. Then I assigned weights to each statistic denoting their importance. The most important statistic is batting average (after all the skill is called hitting for average) so I gave twice as much weight to batting average as the other numbers:
0.4 x BA + 0.2 x contact% - 0.2 x KPCT + 0.2 x LD%
Finally, I reverse normalized the result so that we get back to the original batting average scale.
The way it works is like this: Edgar Renteria had only a .270 batting average. However, his contact, strikeout and line drive rates were all very good. So, his adjusted batting average goes up to .284. The results for all Tigers are listed in Table 5.
Table 5: Tigers hitting for average summary in 2008 player | avg | contact % | K/AB | line drive % | adjusted avg |
Placido Polanco | .307 | .927 | .074 | .187 | .304 |
Magglio Ordonez | .317 | .851 | .135 | .204 | .299 |
Carlos Guillen | .286 | .862 | .160 | .202 | .285 |
Edgar Renteria | .270 | .856 | .127 | .222 | .284 |
Miguel Cabrera | .292 | .775 | .205 | .196 | .275 |
Curtis Granderson | .280 | .796 | .201 | .191 | .271 |
Gary Sheffield | .225 | .830 | .199 | .143 | .245 |
Marcus Thames | .241 | .743 | .301 | .170 | .239 |
Brandon Inge | .205 | .758 | .271 | .164 | .227 |
Renteria and Sheffield both had significantly better adjusted batting averages than real batting averages. Magglio Ordonez and Miguel Cabrera had adjusted BA which were signficantly lower that their real averages. Finally, according to this algorithm, Polanco was the most skilled Tiger at hitting for average in 2008 and Brandon Inge was the worst.