Daniel Shirey/USA Today Sports
Andrelton Simmons makes both the good play and the great play.The most common complaint we run into when discussing advanced defensive metrics is that there isn't a full grasp of how these ratings are computed.
With the help of Baseball Info Solutions, we're going to write a few articles that attempt to go "under the hood" when it comes to looking at advanced defensive metrics.
Most Defensive Runs Saved
SS since 2012
In other words, why does a player rate as well or as poorly as he rates?
We're going to begin with a look at the amazing stats compiled by Atlanta Braves shortstop Andrelton Simmons.
Simmons is a player for whom there is agreement between the scouts and the advanced stats. Scouts describe him as an amazing defender. The numbers show that to be true.
Entering Wednesday, Simmons had played 680 innings in his major league career and the Baseball Info Solutions (BIS) numbers have him with 30 defensive runs saved. He had 19 in 426 innings last season and already has a major-league best 11 in 254 innings in 2013.
For a little perspective, that's an incredible number for what amounts to less than half a season's worth of play. No shortstop has had 30 defensive runs saved in a full season since Troy Tulowitzki had 31 in 2007.
So how do you accumulate so many defensive runs saved so quickly?
But it also helps when you almost always make the play you should make.
The defensive runs saved stat relies heavily on a measure of how often a player turns a batted ball into an out. BIS video-trackers chart every batted ball from every game, labeling where the ball was hit and how fast it was traveling. They can thus assign every ball a value, of how often it was turned into an out.
If a fielder makes a play on a ball in which players at his position made an out 75 percent of the time, he receives a credit of 0.25 (1.00 minus 0.75, to account for being better than 25 percent of fielders ). If he fails to get the out, he is debited 0.75 points (losing value because 75 percent were able to make the play.
Highest Conversion Rate
50+% Plays (SS Since 2012)
We're regularly wowed by Simmons' ability to make the great play. Those plays we linked to are balls that are hits 70 percent and 92 percent of the time, respectively.
But a separator for him is how often he makes the good-to-routine play. BIS looked at every opportunity a fielder had to make a play on a ball in which others at his position recorded an out at least half the time. Since the start of last season, Simmons got outs on 230 of those 244 balls -- a 94 percent conversion rating.
The next-best among the top 50 shortstops in chances was Pete Kozma at 91 percent, which for Simmons makes him about eight plays better than the next-best player. The average shortstop among the top 50 had a conversion rate of 86.5 percent, meaning they would have gotten about 19 fewer outs than Simmons.
Then there's the shortstop the Braves started last season with -- Tyler Pastornicky. His conversion rate was only 73.1 percent -- the worst of any of the 50 checked. A player with a 73 percent conversion rate on 244 chances would get 178 outs. That's 52 fewer than Simmons!
Here's one other stat to consider with regard to Simmons' difference-making abilities.
Last season, in Atlanta's first 32 games, opposing hitters had a .321 "reached-base" percentage (hits plus errors divided by at-bats) when they hit a groundball to the left of the second-base bag. This season, in the first 32 games, their reached-base percentage on grounders to the left of the second-base bag was only .206.
Point being: These metrics don't just pull numbers out of thin air. There are reasons each player has the value he does. We look forward to sharing more of this with you as the season progresses.
Scott Spratt from Baseball Info Solutions contributed research for this article.