Players: Defensive Ratings

Players should be assigned defensive ratings only for the positions they normally play. All positions have a range rating that reflects the player's ability to reach batted balls and turn them into outs and an error rating that reflects his tendency to make errors. Throwing ratings are assigned to catchers and outfielders. Catchers also have passed ball ratings.

The defensive ratings are grouped in a box in the upper-right corner of the player ratings form:

Range rating

This rating indicates a player's ability to reach balls hit in his direction and turn those batted balls into outs. Most baseball announcers use the "range" to mean the ability to cover ground, and that's certainly an important part of what goes into our range ratings. But it's not the whole story.

Our range rating (which takes values from Excellent to Poor) measures each fielder's overall playmaking ability (minus his tendency to commit errors, as we have a separate rating for that). Playmaking ability is not just about range, it's also about positioning, handling the ball cleanly, throwing quickly and accurately, and making good decisions about where and when to throw the ball.

For modern seasons, we carry out very extensive studies of play-by-play data when assigning our range ratings. We look at each player's individual performance on the balls hit his way, overall team defense, the effects of neighboring fielders (3B often take balls that the SS could have handled anyway, so we don't punish the SS for failing to make those plays), and ballpark effects.

Unfortunately, good fielding data can be hard to get for past seasons. The best sources we've found are the team section of the Macmillan Baseball Encyclopedia and the STATS All-time Major League Handbook.

By comparing putouts (for outfielders) and assists(for infielders), and adjusting for playing time, you can get an idea how a player compares with his peers. These types of measures (commonly known as range factors) can sometimes be very misleading, however, as they don't take into account the groundball/flyball nature or left/right mix of the pitching staff. The more of these factors you can take into account when assigning range ratings, the more accurate your ratings will be.

Error rates

This rating is a percentage indicating how this player's error rate compares to the average fielder at his position in the era in which he played. A rating of 100 means the player is average -- that is, he makes 100% of the errors expected of someone at that position. A player who makes only 50% as many errors as his peers is rated 50. Someone who makes twice as many errors as his peers is rated 200.

The following table summarizes how error rates have changed over time, in five-year intervals. Each entry in the table is the number of errors made per 100 full games (or 900 defensive innings).

This table shows the errors per 100 games (900 defensive innings) over time by position.

For example, to assign an error rating to a shortstop from 1912, determine how many errors that player made per 100 games. Suppose the player made 39 errors and was the shortstop about 80% of the time. Based on a 154-game schedule, that's about 123 full games. In 100 games, he would have made 39 x 100 / 123 = 32 errors. Looking at the rows for 1910 and 1915 in the table, we can estimate that the average shortstop in 1912 made 43 errors per 100 games. Our shortstop's rate is 32, which is 74% of 43, so his rating is 74.

Outfielder throwing

The strength and accuracy of an outfielder's throwing arm are indicated in this rating, which is used whenever a runner tries to take an extra base on a single, double or fly ball. These ratings take values from Excellent to Poor.

When we assign throwing ratings for modern outfielders, we use detailed information about the number of extra bases opposing runners took on singles, doubles and fly balls hit to that outfielder. We also look at the number of runners thrown out, but outfielder assists can be misleading. Some outfielders pick up meaningless assists on plays where one or two runners score on a weak throw to the plate, and the batter is retired when the throw is cut off.

If you are assigning throwing ratings for past seasons, we suggest you compare assist totals across the league. Generally speaking, the higher the assist total, the better the throwing arm. This is not always true, of course, because some outfielders have such a great reputation for throwing that nobody tries to run on them (meaning their assist totals are low). So you will need to use some judgment here.

Catcher throwing

This rating indicates the strength and accuracy of the catcher's throwing arm and is used whenever a runner tries to steal second or third. It has values from Excellent to Poor.

When we assign catcher throwing ratings for modern seasons, we use detailed studies of play-by-play data to see how often opposing runners challenged each catchers arm and what percentage of those runners were thrown out. Our studies take into account any SB that were credited to trailing runners on double steals and how often a runner was caught stealing as a result of a pickoff throw by a pitcher. Most importantly, we look at the performance of each pitcher-catcher pair, an approach that helps us determine whether it's the pitcher or catcher who deserves the credit or blame for the results.

When assigning throwing ratings for past seasons, you can start by comparing assist totals across the league. Keep in mind, however, that the best throwing catchers often have lower assist totals because opposing runners don't run on them in the first place.  As is the case with all DMB ratings, you will need to use some judgment.

Passed ball rating

This number indicates how many times a catcher will allow a passed ball in 1,000 plate appearances with runners on base. The formula is similar to that for wild pitch ratings for pitchers:

  rating = (passed balls * 1000) / (batters caught * .43)

Official statistics don't include batters caught, so you'll need to estimate it. For example, if a team's pitchers faced 6300 batters and this catcher was behind the plate 72% of time, he caught about 6300 * .72 = 4536 batters.

The .43 factor indicates that about 43% of all plate appearances occur with runners on base. This number rises and falls with the level of offense in the league.

Playing out of position

You can use a player at a defensive position for which he is not rated, but his performance will suffer. How much? It depends.

Players can make a relatively painless transition to an easier position that is similar to one they're already rated for. The penalties are much greater for moving to a very different position that is also more difficult to play.

For example, a CF can play LF or RF without suffering. Both positions are similar and easier than the one he's rated for. A LF or RF moving to CF has a more difficult time because there's more ground to cover. Similarly, a move from SS to 2B won't cost you too much, while a move from 2B to SS will hurt more. And the moves that will hurt the most are (a) from any position to catcher, (b) a catcher moving to any position except 1B, and (c) a 1B moving to CF or another infield position.

How will these penalties show up? In lots of ways. More balls in their zones will go for hits. They'll make more errors. Guys without outfielder throwing or catcher throwing ratings will be easier to run on. Unrated catchers will have more passed balls. Unrated middle infielders won't start as many double plays on balls hit to them, and they won't turn two as often when they're the pivot man on the play.

You might ask why we don't improve ratings when a player is moving to a less difficult position. Couldn't a top-rated SS play 2B even better than the average 2B? In the many years that we've been assigning fielding ratings, we've seen a lot of players get better ratings when they make the transition from a harder position to an easier one (especially SS -> 2B, 3B -> 1B, and CF -> LF), but we've also seen plenty of cases where the player needed some time to learn how to play the new position.

Every position requires of a different set of skills. A CF moving to RF needs to learn how to play the caroms on balls hit down in the corner. A 3B needs great reflexes to handle the hot smashes that come his way, and that might not be the strong suit of a middle infielder moving to 3B. A SS moving to 2B must learn how to make the pivot with his back to the runner.

If our out-of-position adjustments assumed that every player could instantly adapt to a new position, even an easier one, we think it would create too many opportunities for managers to abuse the game by moving players around in ways that real-life managers would never get away with. So the game imposes penalties of varying degrees on all but a very few out-of-position players.  The exceptions are (a) center fielders moving to a corner outfield spot, who do not suffer a range penalty or a change in their error rate, and (b) shortstops moving to other infield positions, who don't suffer a range penalty but are given an error-rate penalty.