Many of you reading this post hung out at this web address a fair bit last year, or you’re new to the experience but have arrived via my Twitter handle, which means you likely have some understanding of advanced stats in baseball. If you don’t, that’s totally cool. You’re welcome here and we have everything you need to get you up to speed. If you’re into figuring stuff out on your own, our Stat Primer page has everything you need. If, on the other hand, you want the quick summary, this is a post for you.
Let’s start with the basics. When measuring offensive value, we tend to use two stats, wOBA and wRC+. The two stats contain very similar properties, but are presented differently with a couple of little tweaks. The reason we use these two stats is because they are more accurate reflections of offensive performance than stats you may know such as batting average, runs, hits, RBI, and HR. We may still use the AVG/OBP/SLG triple slash line from time to time, but for the most part it’ll be wOBA and wRC+.
The idea behind both of those numbers is that 1) walks matter 2) all hits are not equal 3) hits do not lead to runs in the 1-2-3-4 ratio that you see in slugging percentage. wOBA properly weighs every offensive outcome and scales it to look like OBP. You can read about it in detail using the link above. For 2014, something like .315 will be average and Cabrera will like in the .420+ range. The link even has a calculator!
wRC+ is based on the same principle, but it does two key things. First, it factors in park effects because spending a lot of time hitting in Colorado is going to boost your numbers relative to hitting at Petco. Second, wRC+ is scaled to league average, so the average hitter is always 100 and every step up is a percentage point better than average, but it’s also set to league average each year, so that you can say a player was X% better than his peers in a given year. We use this one quite a bit, so get acquainted.
For baserunning, we like BsR, which is the number of runs you add based on your stolen bases and baserunning. Most of sabermetrics is based on calculating the degree to which something aids in scoring runs, and then those runs are converted to wins. We have UZR and DRS which are run value measures of defense relative to league average.
If you can grasp the concept of wOBA and the concept of run values, you’re probably 75% of the way there. Which makes this a good time to mention that this is a great place to ask questions. You can learn this stuff on your own, or I can help. Comment anywhere on the site, hit me on Twitter, or email us at NewEnglishD at gmail and we’ll take care of you.
For pitchers, we’re going to spend a lot of time using things like strikeout and walk percentage, ground ball percentage, and two stats called FIP and xFIP. These stats churn out an estimate of what a pitcher’s ERA should look like based on their K/BB/HR rates, or in the case of xFIP, those three things plus their fly ball rate and the league average home run to fly ball rate. This tends to give us a better idea of how a pitcher performed independent of the quality of their defense and luck, because we know a lot of what happens on a ball in play is just dumb luck. Both of those pages have detailed descriptions and calculators as well. From time to time, we’ll also employ FIP-, which is simply FIP scaled to league average with 100 being average and lower numbers being that percent better than average.
Both of those sets, for hitters and pitchers, then produce something called Wins Above Replacement (WAR)/calculator, which is a big part of the site. WAR, which you can read about at the link, is how many wins a player is worth compared to a readily available minor league free agent/AAA player. Mike Trout is a 10 WAR player, Cabrera is a 7 WAR player, Don Kelly is like a 0.5 WAR player. You get the idea. If you’re reading something at this site, we’re using FanGraphs’ version of WAR (fWAR), but Baseball Reference and Baseball Prospectus each have their own calculations.
This was just a quick hit to make you aware of the things you’ll need to know to make the most out of your time here, but if you want to learn more, click the links and ask questions. If you have an idea about wOBA, wRC+, BsR, UZR/DRS, FIP, xFIP, and WAR, you should be able to follow everything that goes on around here.