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Explaining Stats: OBP

March 23, 2011
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The last few years we have seen a rise in new baseball statistics. The traditional statistics like wins, RBI, and average have all seen their values dip. Many people hate this change, and see an over complication of baseball with all these new statistics replacing old favorites.

Some people have became downright angry by these changes, but if these stats weren't so effective then why would they have so quickly taken over how teams and scouts evaluate players? At the end of the day these new stats, and the math whizzes who have designed them, have changed the way players are evaluated. These stats like every other stat are there to help figure out who are the most effective players in the league when you compare them.

My goal here is to explain these stats so everyone can understand them better and make them something that everyone can reference. Since there has been such an explosion of new stats, I am going to start with new hitting stats, then do pitching, and lastly combined stats. I might also do fielding stats after all of them, but the issue with fielding stats is that no one agrees on them because there isn't a go to stat in fielding as of yet that is consistently effective.

For this article I am going to explain on-base percentage. Over the course of these articles if I miss a stat, someone wants me to do a different stat next, or if there is something anyone wants explained better then please comment in this post and I will try and explain as best as I can.

Before I get too in depth I want to go ahead and label the abbreviations that will be appearing over and over. OBP is on-base percentage, BB is walks, SF sacrifice flies, H hits, AVG is average, HBP is hit by pitch, AB is At bats. I know many of these are basic abbreviations, but rather than assume I figure I would spell them all out now. Also when I mention last year's percentiles, I have to give credit to fangraphs for that data.

Now let's get onto the new stats.

The first stat to be discussed is the one that most people are probably the most familiar with, on-base percentage. It is so main stream now that it's seen on scoreboards. The reason this stat has risen is that people have started to realize how important walks are and that batting average completely ignores the value of a walk. This stat is figured out by adding BB, HBP, and H and then dividing by the total of AB, HBP, and SF.

If it was written out it might look like this (BB+HBP+H) / (AB+HBP+SF).

I have often considered .380 or better to be excellent. For those who want a reference point I consider it in line with what people view as a .300 hitter. In terms of last year, .385 was good enough to make the 90th percentile last season. Outfielder Shin-Soo Choo's OBP was .401 and good enough for 4th best in the AL. Worst on the Indians was infielder Jhonny Peralta with an OBP of .311, good for 12th worst in the AL.

Now let's play a game of who would you rather have:

Player 1: AVG .260 OBP .378
Player 2: AVG .282 OBP .313
Player 3: AVG .302 OBP .351
Player 4: AVG .238 OBP .346

So who do you want on your team? Many old school fans might say give me the .300 hitter, but if you take that player he is actually reaching base a lot less. Sure he has an average that is 40 points higher, but his OBP is over 25 points lower. This is the problem with just relying on average as you cut out a significant cross section of data. I know people can and do argue a hit is more valuable as it can move a runner more than one base, but is it worth a player reaching base less times a year?

Player 2 is the patron saint of no patience, Alexi Ramirez. His OBP was only 2 points higher than Peralta who hit 32 points lower than him, again showing that average paints a partial picture.

Player 4 is Ben Zorbist who in spite of hitting 44 points lower than Ramirez actually reached base significantly more, and reached base almost as much as player 3 even though player 3's average was 64 points higher.

Player 3 is former Indian Victor Martinez, who I would worry about as a Tigers fan. As many players age those that hold up the best tend to have the best strike zone judgment, and Martinez's walk totals show he is a bit of a free swinger.

Player 1 is possible one year wonder Jos

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