## Better Know A Stat - OPS+

Inspired by Stephen Colbert and his Better know a congressman series, TBLA is launching our new "Better Know A Stat" series and today's debut is the baseball reference stat OPS+. OPS+ is a great stat to start with as we use it just about every day, and it incorporates several stats that everyone should know. OB%, Slug%, and OPS. From The Baseball Page Website

OPS+ is OPS adjusted for the park and the league in which the player played, but not for fielding position. An OPS+ of 100 is defined to be the league average. An OPS+ of 150 or more is excellent, and 125 very good, while an OPS+ of 75 or below is poor.

A common misconception is that OPS+ closely matches the ratio of a player’s OPS to that of the league. In fact, due to the additive nature of the two components in OPS+, a player with an OBP and SLG both 50% better than league average in those metrics will have an OPS+ of 200 (twice the league average OPS+) while still having an OPS that is only 50% better than the average OPS of the league.

Many of you understand the definition above but for those that don't let us take a look at each of the statistics being used in the formula, which is basically:

### On Base Percentage

OB% is measured by the sum of hits (H), base on balls (BB), and HBP (hit by pitch)  divided by the sum of times at bat (AB), (BB), sacrifice flies (SF), and HBP. The formula looks like this (H + BB + HBP) / (AB + BB + SF + HBP). If you have been here anytime at all you know that we usually use OB% instead of batting average when discussing the offensive potential of a player.  Each person has loyalties to certain statistics, some have discounted the batting average as obsolete but it is hard for some of us to give up that ghost, however OB% factors in every time that a hitter reaches base safely, not just the time the batter gets a hit and is much more indicative of a the offensive value then batting average. Using Matt Kemp in our example:

(180+52 + 3) / (606+52+6+3) = .352

.350 is good not great but when combined with Kemp's power you have a valuable player. Jamey Carroll and Russell Martin have good OB% but a weak slug% with little speed to go with it, making them much less valuable from an offensive standpoint.

### Slugging Percentage

The 2nd part of the OPS is the slug%  which takes the total bases (singles (+1), doubles (+2), triples (+3), home runs (+4) ) divided by at bats. The forumula for slug% would be (Total Bases ) / (AB). Again using Matt Kemp as an example Matt had 122 singles, 25 doubles, 7 triples, and 26 home runs.

((122*1) + (25*2) + (7*3) + (26*4)) / 606  = .490

.490 is great for a center fielder. Only Tori Hunter had a higher slug% then Matt Kemp in 2009 for centerfielders.

### On-Base Plus Slugging (OPS)

Adding OB% with Slug% gets you OPS. This statistic is credited to Bill James,  It is designed to merge a player's OBP, which measures how often he gets on base, and his Slugging Percentage (which measures ability to hit for average and power).  Until more advanced metrics came into play this is the stat that many used and still use when trying to determine the offensive value of a player. It has some good things and bad things. Stolen bases are completely ignored and it weights the OB% the same as Slug%. Also it does not normalize for era's and ballpark effects. For example Wes Parker had an OPS in 1970 of only .850 which at first glance is a good year for a first baseman but not really a great year. If you were to sort LA Dodger first baseman by OPS his .850 would be the 10th best offensive season. However when you use a normalized stat like OPS+ his season is actually tied for 3rd best. It was one hell of a season but the numbers are masked behind the tough hitting environment of Dodger Stadium.

That is why we love to use OPS+, it uses OPS but then normalizes the numbers for era and ballpark effects allowing you to compare what someone did in 1970 with what someone did in 2009.  OPS+ still has the same problem of weighting OB% and Slug% equally and more complex metrics have become available to address this but for a quick and dirty way to compare players across leagues and era's, it makes for a great metric.

Below are the 17 greatest Los Angeles Dodger seasons according to OPS+.

`                                                                              Player           OPS+  TB Year Age  AB HR RBI  BB   BA  OBP  SLG   OPS     PosMike Piazza       185 355 1997  28 556 40 124  69 .362 .431 .638 1.070    *2/DPedro Guerrero    181 281 1985  29 487 33  87  83 .320 .422 .577  .999 *7538/9Gary Sheffield    176 322 2000  31 501 43 109 101 .325 .438 .643 1.081    *7/DReggie Smith      167 281 1977  32 488 32  87 104 .307 .427 .576 1.003    *9/8Mike Piazza       166 308 1996  27 547 36 105  81 .336 .422 .563  .985      *2Gary Sheffield    164 300 2001  32 515 36 100  94 .311 .417 .583 1.000   *7/D9Adrian Beltre     163 376 2004  25 598 48 121  53 .334 .388 .629 1.017    *5/6Reggie Smith      161 250 1978  33 447 29  93  70 .295 .382 .559  .942    *9/8Eddie Murray      158 290 1990  34 558 26  95  82 .330 .414 .520  .934      *3Pedro Guerrero    156 308 1982  26 575 32 100  65 .304 .378 .536  .914    *985Shawn Green       154 325 2002  29 582 42 114  93 .285 .385 .558  .944    *9/DShawn Green       154 370 2001  28 619 49 125  72 .297 .372 .598  .970   *9/83Kal Daniels       154 239 1990  26 450 27  94  68 .296 .389 .531  .920      *7Pedro Guerrero    154 294 1987  31 545 27  89  74 .338 .416 .539  .955     *73Mike Piazza       152 307 1993  24 547 35 112  46 .318 .370 .561  .932    *2/3Jimmy Wynn        151 266 1974  32 535 32 108 108 .271 .387 .497  .884      *8Pedro Guerrero    150 310 1983  27 584 32 103  72 .298 .373 .531  .904    *5/3`

Provided by Baseball-Reference.com: View Play Index Tool Used
Generated 12/30/2009.

The purpose of this series is not for our regular commentators who are already well versed in modern statistics but for those of who have found our site, hang around but don't quite know what we are talking about. This series would be a good time to ask questions and we will do our best to answer them.

Also I'm no expert so if I have made any mistakes or misrepresentations, please let me know so I can fix them.

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