Sabermetrics is the search for objective knowledge about baseball (the term was coined by Bill James, the most famous sabermatrician of them all). James chose this term as an homage to the group of people who study the history of the game of baseball – the Society of American Baseball Research (SABR). Sabermatricians don’t say ‘Justin Upton is better than Alfonso Soriano because he has a prettier looking swing,’ they say something like ‘Justin Upton is a better hitter than Soriano because he ranks higher than Alfonso in the following categories the last two years...’ Sabermetrics uses objective data and not subjective opinions to develop their conclusions. In this piece we'll focus on one of those measures used in sabermetics – Secondary Average.
NOTE: Make sure you check out Bases Per Plate Appearance that was written about previously.
SECONDARY AVERAGE DEFINED
Secondary Average, or SECA, is a sabermetric tool used to gauge a player’s ability to produce extra bases independent of batting average (the total of a player's extra bases earned on hits, walks and stolen bases expressed as a percentage of at-bats).
The idea behind the measure is simple. Does a .020 point advantage in batting average for Player A mean he is a better hitter than Player B? Of course not if Player A has 14 home runs while Player B knocks 36 long balls. In essence, SECA attempts to fill in the gaps that batting average doesn’t directly address. As a result, SECA basically covers the three primary factors of an offensive contribution outside of average: power (bases), eye (BB) and speed (SB).
What sets SECA apart from other simple metrics is that it takes into account various aspects of a player’s offensive contribution including two lesser-recorded measures when it comes to judging a players overall offensive effectiveness; the walk and the stolen base. Any time a player gains a base without making an out he should be rewarded, and that’s what SECA attempts to do.
Here is the equation that is used to figure SECA.
(TB - H + BB + SB) / AB
Here is an example so you can see how easy it is to figure SECA.
In 2013 Adam Jones produced the following numbers for the Orioles.
322 Total Bases, 186 Hits, 25 BB, 14 SB, 653 AB.
(322-186+25+15) / 653
176 / 653
SECA = .269
So what SECA records is that in 2013 Jones' offensive contribution produced an SECA mark of .269. For comparisons sake, the league average SECA mark was .250, just one point lower than the league batting average of .251 in 2013.
To place the numbers on a spectrum of effectiveness, a fantastic season in SECA results in a mark above the .450 mark, a mark over .400 is impressive, again .250 is the league average, while a number below .200 is considered to be a poor showing (guys under .200 can still be good fantasy performers if they steal bases and help in the batting average categories).
It should also be noted that there is quite a bit of volatility in SECA. It varies much more than batting average for example. It's not a tool to use predicatively, at least not on it's own. It needs to be paired with other measures to paint a picture, though it is a good tool to look at how a player got to where he is right now.
Which brings up one last point. Why use at-bats in the equation and not plate appearances? Well you just read why. Basically, at-bats are used because they allow the SECA mark to closely mirror the major league batting average in most years. With that, let's get down to breaking down the players.