Isolated OBP

The other day I was thinking about the metric ISO (Isolated Power) which is SLG minus AVG and thought about what a metric of OBP minus AVG would tell us. Of course someone already thought of this, namely Michael Salfino of The Athletic here. It always seems like someone smarter thinks of the good ideas first but let’s take a deeper dive into the 2023 data.

So what does this Isolated OBP (ISO OBP) actually tell us? Well it gives us a measure of how much a player depends on hits to get on base. This means the lower the ISO OBP the more dependent on hits the player is to get on base. Hits have a lot of randomness to them so they are not as reliable as a hitter’s eye at the plate to get on base. A player could be in a slump at the plate but still get on base due to their ability to get a walk. Ideally a leadoff hitter would have a higher ISO OBP.

Let’s dig into the data!

	Name	BA	OBP	ISO	ISO OBP
1	Kyle Schwarber	0.191	0.335	0.274	0.144
2	Ryan Noda	0.239	0.381	0.181	0.142
3	Juan Soto	0.261	0.401	0.228	0.140
4	Matt Carpenter	0.174	0.314	0.129	0.140
5	Max Muncy	0.205	0.333	0.280	0.128
6	Jose Caballero	0.227	0.355	0.095	0.128
7	Jack Suwinski	0.206	0.333	0.236	0.127
8	Aaron Judge	0.265	0.392	0.362	0.127
9	Joey Gallo	0.173	0.300	0.257	0.127
10	Andrew McCutchen	0.250	0.373	0.138	0.123

Looking at the top 10 in ISO OBP we see players we’d expect like Juan Soto, Aaron Judge, Kyle Schwarber, and Max Muncy with superior plate discipline. We also see the three true outcome (homerun, walk, strikeout) players in Kyle Schwarber and Joey Gallo. Of these players, 6 out of 10 have led off this season.

We can see that if we take ISO (Isolated Power) into consideration there are players with very weak ISO but high ISO OBP. In an ideal world you’d like to maximize both and you get players like Schwarber, Soto, Muncy and Judge. I believe that these are your ideal leadoff hitters because they get on base via a walk and when they hit the ball it is likely that extra bases are involved. There could be an argument to be made that batting them second (like Judge for example) is the best because they can drive in more runs. To which I’d argue that if you don’t have a hitter in front of them that has a high ISO OBP then you will not have as many runners in front of them over the course of the season. The ability to drive runners in is a different story for a different blog post.

The Moneyball adage is getting on base leads to wins. Higher ISO OBP shows a hitter has a good eye and will get on base without depending on a hit. Ideally you maximize both ISO and ISO OBP for a leadoff hitter but a high ISO OBP should lead to more times on base in the long run.