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Staturday: UZR, DRS, and Def

Today we kick off the different fielding stats. UZR, DRS, and Def are (and hopefully were) the three most used stats when looking at a player's defensive season. Now before I go on and breakdown these three stats, there is something I have not brought up much when talking about all the stats and that is sample size. Sample size is one of the most important things to understand when analyzing players. The more samples there are, the more you can trust a stat. For example, a guy hitting .400 over a week is a lot less impressive than a guy hitting .400 over an entire season. Sample size and defense go hand-in-hand. Looking at a guy's defensive statistics over multiple seasons is heavily encouraged if you are trying to figure out if he is a good fielder or not.

The first stat we are going to look at is UZR and it stands for Ultimate Zone Rating. I am not going to go in-depth on how UZR is calculated but it looks at things like how much range does a player cover, are they prone to committing errors, if they're an infielder how good they are at turning double plays, and if they are an outfielder how good is their arm. When looking at UZR, the higher the number the better the fielder and if you see a negative sign then they are below average (0 UZR). You may see a stat called UZR/150 and that just tries to average a number closer to the average amount of times a player makes a play in a season (150 attempts).

DRS stands for Defensive Runs Saved (this is my preferred choice of the three stats) and just like UZR, it has many components that factor in. I won't list all of them but it does take into account double plays, how well a fielder handles bunts, and does an outfielder rob a homer. It also functions on the same scale so that should make it easy to remember.

Both UZR and DRS tell you how many runs a player prevents (or allows) compared to other players at his same position. That means you can compare Kris Bryant's defense to Nolan Arenado's defense but you can't compare Kris' defense to Anthony Rizzo's defense. Let's take a look at Javy's defensive values at shortstop for his career.

I think we can all agree that Javy is a great defensive shortstop but looking at these numbers we see a lot of negative values. This is why I said earlier that we need to be aware of sample sizes. 45 innings at shortstop is nothing compared to over 1,000 innings. A single bad play could greatly lower your stats. We also see that there can be discrepancies in the different stats like in 2017 and 2018 when Javy had negative UZR stats but positive DRS stats. Each stat cannot tell us the entire story so it is good to compare multiple defense stats against each other and to also compare them against multiple seasons.

Our third and final stat for today is Def (Defensive Runs Above Average) and it is just like the two stats we have talked about. In fact, it actually uses UZR in its calculations. So how the heck is it different from UZR? Well Def uses a positional adjustment value so you can use it to compare all player's Def values regardless of their position. Some positions are worth more defensively than other for example a shortstop will have a higher adjustment weighing than a right fielder. This unique feature of Def allows it to be used in the WAR calculations (we will cover this before the start of the season). Because it uses UZR, it functions on the same scale as UZR and DRS. Below is Javy's Def stats for his career.

These Def values encompass all of Javy's defensive positions throughout his career, not just his time at shortstop. We see that Javy has pretty much always been a plus defender (sixth best in 2019).

So those are the three defensive stats we will be covering today. Remember that the higher the number, the better the defender for these stats. Also remember that Def stats can be compared to any defender in baseball while UZR and DRS can only be compared to players at the same position. The next two weeks we will be looking at some newly created stats thanks to Statcast and defensive stats that I hope take over the game. Tune in next to find out why I hope that.


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