Understanding Baseball's New Advanced Offensive Metrics
It is no secret, baseball is changing before our very eyes. Turn on a game right now and you will see a clock counting down how much time a pitcher has to throw the next pitch. That seems counterintuitive to the sport of baseball, which has always had the reputation of being a slow, methodical game with no time limit. While I may get into the rule changes in the future, that's not what we're doing here. We're here to look at the behind-the-scenes changes that were at the forefront of baseballs "analytical movement". The new analytics have led to differences in scouting, lineup construction, and front office decision making. It's a simple shift in how baseball is being evaluated from a statistical standpoint.
My intent here is to just give a comprehensible rundown of all the fancy new metrics that are becoming more prevalent in the baseball world. As an aside, I have played baseball my whole life, still do, and have grown up in an "old school" baseball household. My dad and grandpa believe in bunts to move a guy over, 2-strike approaches, and that command on the mound trumps velocity. I think I have some of those values instilled in me, but I have also seen how the "new school" approach is taking over baseball and making players better than we have ever seen. So if you can't beat 'em, join 'em. I'll start by explaining why some of the traditional hitting metrics are becoming obsolete, before diving into what the advanced metrics and why they may paint a bigger picture. I am not forcing anything down someone's throat here; you can be your own judge on whether you like it or not. But at least you will have a clue next time someone throws around xwOBA at your family gathering.
Offensive Metrics - Why Average Isn't so Important Anymore
I told you I was going to start with some of the metrics that are no longer viewed as being important or at least not nearly as important as they once were. That lands us right at the stat that used to be the first thing we'd look for on the back of a baseball card, batting average (AVG). The "nerds" in baseball no longer care about AVG. I know it seems silly; for as long as I have played, and even still now, I aspired to be a .300 hitter. It's not a good feeling to have the ol' batting average start with a 2. But there is good reason why AVG doesn't matter much anymore. Let's compare two fictional hitters in a full season.
To start, we're assuming both hitters walked 60 times and neither hitter had a triple (for convenience). Hitter A had 180 hits in 600 AB's. Of his 180 hits, he had 150 singles, 20 doubles, and 10 HR's. Hitter B went 150/600, but of his 150 hits, he had 30 doubles and 30 HR's. Hitter B had 30 less hits, but 10 more doubles and 20 more homers, so 40 more total bases. The name of the game on the offensive side is run creation (we will see this term come up a lot). A single rarely scores a runner from first, but a double might, and a HR certainly will. While hitter A obviously has more hits, Hitter B had more bases and more HR's, making it much more likely that he drove in more runs and even scored more runs himself (it's easier to score after a double than a single!). While AVG still matters, it really is about those extra base hits that can help produce runs more. Especially against the nastiness of pitchers today, if a hitter is only going to square up one pitch a game, you'd rather it be in the gap or over the fence than over the pitchers head for a single.
Offensive Metrics - The New School
Now that we have talked about why AVG is less important, I would like to dive into some more advanced metrics. I will try to be brief on each to just give an overview of them. For a more thorough explanation of these metrics, there are plenty of resources and expansive research available online to make a deeper dive. If you are interested in this, I would definitely recommend looking further into it. Personally, I think it's pretty fun to poke around these metrics and see how helpful some of them can be.
1. Exit Velocity and Launch Angle
We start with two of baseball's new favorite buzzwords, but don't let this confuse you. These are not fancy new metrics although many people make it seem like they are. Exit velocity literally is just how hard someone hits the ball. Launch angle is the angle at which the ball comes off the bat. Now there is optimal exit velocity (as hard as you can hit it) and launch angle (between 10-30 degrees, aka a low line drive or a high line drive / low fly ball). But every single batted ball has an exit velocity and a launch angle. Heck, even a bunt does. A ground ball has a negative launch angle, a pop up has a launch angle basically 50 degrees or higher. Again, people like to make a big deal that today's hitters have 'launch angle' swings. Well every swing produces some launch angle, so that's just silly. These two metrics just make the old phrase "hit it hard and on a line" measurable.
2. SLG, OPS and OPS+
You may have spotted SLG and OPS in our example hitters. Did you notice how hitter B, who has a lower AVG but is potentially deemed more 'valuable,' had a higher SLG and OPS? SLG stands for slugging percentage, and is simply total bases divided by total at bats. It tells more of the story of how much power a guy has. OPS stands for on-base plus slugging. You'll never guess how they calculate this one! It is the hitters OBP (on-base percentage) + his SLG. I truly believe this is the simplest form to measure a hitter now because it's like average but it accounts for walks and extra base hits.
OPS+ just normalizes a hitters' OPS throughout the league. This means it puts all hitters on a scale that season, where the average hitters OPS gives him an OPS+ of 100. That means an OPS+ of 150 makes him a '50% better than league average' hitter for that year, so on and so forth. This helps paint a better picture because, for example, in 2017 when the baseballs were 'juiced up' a bit, OPS was up across the league for almost all hitters. By standardizing OPS with OPS+, we account for things like this, as well as any other factors like which ballpark hitters played in (a player hitting at Yankee Stadium or Coors Field usually has better numbers).
Now that we've learned SLG, ISO is actually quite simple. It is calculated by subtracting AVG from SLG. In doing so, it becomes a metric that measures how much of a hitters SLG comes from their AVG. The higher the ISO, we assume the hitter is more of a pure power hitter (less singles, more XBH's). The lower the ISO, we assume more of a singles hitter. As it stands, Patrick Wisdom is the MLB leader in ISO at .446 (as of April 21, 2023. Stats subject to change as the season progresses). This is not surprising, because he has 17 hits this season to date, 12 of which are extra-base-hits (3 doubles, 1 triple, 8 HR's). That is the definition of a power hitter.
wRC+ stands for weighted runs created plus. This is another metric that is 'normalized' across the league to account for factors like ballparks, eras, leagues, etc. I don't want to dive into how it is calculated because it takes some complicated mathematics. So just take my word for it here. The overall essence of wRC+ is to quantify run creation. I mentioned earlier how the name of the game is creating runs. Thanks to the 'math nerds' in baseball, this statistic (presented on the same 100 scale as OPS+ in terms of being average, above, or below) helps us quantify the value of a hitter in terms of run creation. As of the aforementioned date, Matt Chapman is the wRC+ leaders in the MLB. To make some sense of this, let's put it in some old school and new school terms: He leads the AL right now in AVG, OBP, SLG, OPS, and OPS+. Yes, that will get the job done in terms of run creation.
5. wOBA and xwOBA
These are the last two offensive metrics we are going to look at. wOBA stands for weighted on base average, and xwOBA stands for expected weighted on base average. The best part is they are pronounced *woah-buh* and *ex-woah-buh* (think wumbo from Spongebob but better). wOBA aims to explain how a runner reaches base, and not just that he reached base. HR's are the most valuable way a hitter can reach base in terms of run creation, while walks are the least valuable. I know it might seem intuitive, but a homer guarantees a run is scored, while walks have the least likely chance to bring in a run (at least a single can score a guy from second). So, in essence, it is just measuring how a hitter reaches base and the value of that method in creating runs (again, runs are everything!).
xwOBA is interesting because it is uses each batted balls exit velocity and launch angle (among other metrics) to determine the expected outcome of that batted ball in terms of wOBA. In other words, it tries to predict what the hit 'should have' been. We all know the beauty of baseball, where a guy lines out 4 times one day and bloops in 4 hits the next day. By comparing wOBA and xwOBA, the difference between the two is basically the purest form to compare how 'lucky' a hitter has been. If a hitter has a much higher wOBA than xwOBA, we can assume that the hitter has been lucky on finding grass on the field, and after some reversion to the mean his numbers will go down. The opposite can be said when xwOBA is higher than wOBA. It is not always the case that wOBA and xwOBA come close to equal at the end of the season, but very often it explains the 'luck' factor a hitter ran into that season.
I hope you enjoyed learning some more about these advanced metrics. I want to reiterate, take these or leave these as you like. If you still believe in the value of a .300 hitter, that is totally fine. All these stats might seem like they overcomplicate the game, and only time will tell. But there is a wave of analytical thinking taking over baseball, trying to find the most efficient way to value runs scored and put that product on the field. If you found some interest in these metrics, keep on learning! There are other offensive metrics, such as BABIP, SWSTR%, WAR, etc, that also play a part in hitting evaluation. Not to mention, there are many new pitching metrics as well that I am sure we will get into in another post. For now, learn these and enjoy being in the know when you watch some baseball this season.