What is WAR, ERA+, OPS+, UZR etc.?

It's likely that many of you reading this have a little bit less knowledge as to the alphabet soup of stats used to track MLB player's performance.  Confusing matters more, I will be using exclusively fangraphs' metrics from this point forward, while still highlighting basic stats like on-base percentage and home runs, just to make these articles simple enough for a fan at any level of sabermetric knowledge.  My reasoning behind aligning myself with the brainiacs at fangraphs.com is simply to streamline my own personal research.  This is not to say that I will not use baseball-reference.com any more; they've done baseball fans, and nerds alike, a tremendous service in their fastidious cataloguing of statistics dating back to the 1870s.  Love love love that site.

Most of you don't even know what that word "sabermetrics" means.  Basically this word defines an ultra-nerdy scientific movement seeking to quantify every facet of baseball through complex mathematical equations.  While I may not be the most versed in the sabermetric ways, I have a good base understanding of the math behind it, and certainly live and die by many of these metrics.  Any of you who read any portion of my season previews can see the alphabet soup I used in evaluating players and teams, so here's a quick look at what each of these stats mean for those of you too lazy to google them.

OPS+:  This is a stat used to measure a player's offensive contributions compared to the league average with a players' home park factored into it as well.  Its base is set at 100 for a league-average player; scores 100> = below average, 100< = above league average.  This metric is extremely close to fangraphs' wRC+, which, as previously stated, I will be using on this blog going forward.

ERA+ (or ERA- in fangraphs):  This is another metric in the vein of OPS+, except it focuses on pitchers' ERA.  It is league/park-adjusted and the 100 mark is used to denote a league-average hurler with anything below 100 being sub-par and above 100 being considered above average.  For ERA-, a lower number is better, but league average is set to 100.

Courtesy of fangraphs.com

UZR:  This metric is used to quantify a player's total defensive contribution and is also league/park-adjusted.  I'm fairly certain that if I even began to explain this stat my head would explode.  At minimum my writings would look like character diarrhea all over your screen.  So here's a chart displaying the breakdown of UZR with 2010 stats used for the percentiles.  Also, here's a link to DRaysBay Editor-in-Chief Steve Slowinski's full explanation of the stat.

UZR/150:  This is the same tell-all defensive metric calculated per 150 defensive games.

Note - both UZR uses can be tricky, because there is quite a bit of inconsistencies on a year-to-year basis due in part to the small sample size of defensive data.  This stat, however, is the best we have currently and I enjoy it thoroughly.

ISO:  Really cool, simple metric.  It's a batter slugging percentage minus their batting average.  It is used to identify how much power a player really has.  (.145 was the 2010 MLB average. Again, courtesy of fangraphs.)

BABIP:  This is a two-way metric, used to look at both pitchers and hitters.  The acronym stands for batting average on balls in play, and means just that.  It measures the number of balls in play that went for hits.  For hitters, this is their batted balls.   For pitchers, it's simply an average of the balls hitters put in play against him that went for hits.  League average hovers around .300, so any hitter that is above it is likely to see a fall in performance.  And, any pitcher that is above .300, has likely been a victim of circumstance, and should see a better ERA down the road.  The stat works both ways for performance prediction; performances above expected levels (give or take .300 for a given season) will likely regress, while those below this number can expect an uptick in their numbers.

WAR:  This is the grandaddy of 'em all!  This is a sabemetricians' attempt to calculate the entire on-field value (offense, defense, baserunning, pitching, etc) for any player and assigning it a value that is equal to the number of wins the player produced above replacement value.  Replacement value is assumed to be a Triple-A call up or their ilk.  There are two camps here; on one side is Sean Smith of BaseballProjection.com, and on the other, is Dave Cameron at fangraphs.  Both metrics work the same way, however, their numbers are always different due to separate calculating methods.  In my previous writings I used Sean Smith's WAR, but will now exclusively use Dave Cameron's method.  So if you see WAR from here on out, you'll know I'm speaking of the stat kept over at fangraphs.com.