Wednesday, August 12, 2009

Advanced Stats- Offense (Part 2)

We discussed how OBP is a better statistic than BA. Towards the end I discussed how Aaron Rowand and another player by the name of Nelson Cruz, have a similar OBP, but Cruz gets more big hits. This difference in power is shown by a statistic called Slugging Percentage (SLG). Slugging Percentage is simply total bases/ divided by at bats. Total Bases are all the bases that a player accumulates. A single is worth 1, a double is worth 2, a triple is worth 3, a home run is worth 4. Walks are not factored into slugging percentage. The average team slugging percentage since 2007 is .419. However, a good/acceptable slugging percentage is really dependent upon which position a player plays. A .420ish SLG may be acceptable for a shortstop, but is almost definitely unacceptable for a first baseman.

So, when we compare the slugging percentages of Aaron Rowand and Nelson Cruz we notice that Cruz has an enormous advantage. Cruz has a .547 SLG compared to Rowand's .436. What does this tell us? It tells us that Cruz is just as good as Rowand in terms of drawing walks and getting on base and is much better at hitting for power. Overall, Nelson Cruz is a better hitter.

Although better than BA, OBP and SLG have their flaws. OBP doesn't take into account extra base hits while SLG doesn't take walks into account. One way that people have combated this problem is by combining OBP and SLG together. This combined statistic is called OPS (On Base Percentage + Slugging Percentage). The formula is calculated exactly how it sounds you take OBP and add SLG together. This stat helps when comparing players with different OBP and SLG. For Example let's use Nelson Cruz again and substitute Aaron Rowand with Jayson Werth.

Jayson Werth has an OBP of .381 compared to Cruz's .337. Werth has a .503 SLG compared to Cruz's .547. When combined we notice that Werth and Cruz have a nearly identical OPS. Werth's OPS is .883 while Cruz's OPS is .884. This suggests that both players are both pretty equal in terms of hitting.
Going back to that league average slugging percentage, we can see that not only is slugging percentage dependent on the position you play but as well as how often you get on base. As stated before a .420 SLG for a first baseman is below average, but if he gets on base at a .420 clip his OPS would be .840. That's pretty acceptable for a first baseman.
But what is more important? Getting On Base more or hitting for power? Is Werth's OBP more important than Cruz's power or is it the other way around. Wait for Part 3 to find out.

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