Total Zone (TZ) in Baseball

What is Total Zone (TZ) in Baseball?

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In the baseball book “Moneyball,” the author laments poor statistics used through the 20th century to judge defensive play: “The statistics were not merely inadequate; they lied,” he wrote. Out of this, around the turn of the century, came defensive measurements like Total Zone.

Total Zone in baseball is a statistical measurement of defensive performance by players as devised by Sean Smith for his in 2008. It’s considered among the best ways to truly judge the effectiveness of defensive players, by considering a whole slew of new data that was unheard of not long ago.

Also known as TotalZone, and shortened often to TZ, this measurement system is considered among the top defensive statistics to compare historical data of MLB games versus recent game play data. Basically, it tries to compare the defensive prowess of players today versus those of yesteryear.

The TZ is not the only statistic to judge the defense of players or teams. Often it is used in conjunction with another stat; or is used as a sort-of barometer for how other measurement systems judge players.

At the time of its release and the years immediately following, the TZ ratings of players was perhaps the most-respected statistical measurement for ballplayers’ defensive skills. That distinction has since been surpassed, but the TZ numbers remain impressive nonetheless.

Shortfalls of Fielding Percentage in Baseball

This all began when some number-crunchers in the 1970s began to challenge a long-established statistic attached to defensive performance by MLB players: fielding percentage.

Also called fielding average, this stat measures the percentage of opportunities a player in the field properly handles a ball struck or thrown to him. It’s calculation looks like this:

Fielding Percentage = Putouts + Assists / Putouts + Assists + Errors

The higher the percentage, the better. A perfect fielder has a 1.000 fielding average, much like a hitter who never makes an out is hitting 1.000. However, a player’s chances to reduce that number increase every time he touches the ball on the field.

All kinds of situations can chip away at that percentage, by increasing the number of opportunities to make an error.

A putout is when a player is the last to touch the ball when out is called, either catching the ball hit into the air by the batter, or catching a ball thrown by another player and either tagging a runner who is not on a base, or stepping on a base to force a runner.

An assist is given to players who successfully throw the ball to another player to make a putout. There are no assists on fly-ball or line-drive outs, nor on strikeouts.

Errors, of course, are assigned to players who fail to complete a putout on a play where he was expected to make the play.

Not every muffed play is officially ruled an error. This is up to the scorekeeper, who can use how hard the ball was struck (liner, grounder, soft floater, etc.), and where it was struck, and the situation in determining whether a play should have been made.

This part of fielding percentage ~ the judgment of a 3rd party about whether or not a play should have been made ~ has plagued the fielding percentage statistic for many decades.

Still, because nothing better was devised to replace it, Major League Baseball continued to use it ~ even announcing fielding percentage winners for each position, and releasing all season numbers to be considered in voting for awards like the league’s Gold Glove Award for defensive players.

Then those guys in the 1970s began asking, “Does fielding percentage actually tell you anything?

Aside from the question of subjectivity with scorekeepers, many questions surfaced about the range of defenders. Players avoiding making errors is fine and dandy, the thought went, but what if they are too slow or unskilled to get to balls in order for a statistic to count?

In short, some players avoid errors by just not having as many opportunities to make plays, compared with exceptional defenders.

Those who cannot get to balls surrender base hits, which do not count against them in fielding average; and that lack of range doesn’t hurt them either. On the flip side, having great range is a big part of being a good defensive player in baseball; yet it meant nothing for fielding percentage.

It took baseball fanatics many decades not just to figure out alternatives, but to aggressively and consistently work toward finding the absolute truth when it comes to stats and judging defenders.

Enter, zones, zone ratings, Total Zone, and more.

Zone Ratings and More About Judging Range in Baseball

These stat-heads, led by baseball numbers guru Bill James, began devising ways to slice up a baseball field, at every MLB stadium, to begin to insert a player’s range into defensive statistical equations.

Basically they began to inspect where balls were struck, and which area (zone) it landed, and assigning probabilities and other measurements for the players in positions near those zones.

This way, a player could not just stand idly while a ball dropped 10 feet in front of them for a hit, and get away with it. If that ball was struck in his zone, and he failed to make the play, he gets penalized for it under modern defensive stats.

First, there was zone rating, which just takes the number of plays a player makes, and then how many balls were hit into the zone in which he was playing. Then simply divide the 1st number by the second figure, resulting in a zone rating.

Today there also are Ultimate Zone Rating (UZR), and Defensive Runs Saved (DRS).

Ultimate Zone Rating considers errors, a player’s range, arm strength in the outfield, and double-play ability. It is much similar to DRS; the statistical concepts are equal, they just use some different considerations.

Total Zone (TZ) is also one of those types of measurements in baseball. With TZ, either current game data like where each ball was struck is plugged into the computer, or researchers dig into box scores or broadcast reports of old games played and plug the data into the same program.

In this way, they can compare defenders of today with those of the past. By the way, the final TZ numbers start at zero, and the larger they are in positive, the better the defensive play. Big negative numbers, like -100 TZ, means terrible fielders. Anything from -2 to 2 is considered average.

Related Questions

Question: Where did Sean Smith release his new TotalZone measurement system?

Answer: Through his interesting, data-packed website, The page that explains defensive statistics can be found here.

Q.: How do MLB players qualify for leaders in career fielding average, if some players have hardly any chances and retire with a 1.000 average?

A.: MLB players must appear in 1,000 games at a position; or pitchers must have thrown at least 1,500 innings.

Q.: Which team had the highest fielding average for a season?

A.: Baltimore Orioles in 2013 finished the season with a team fielding percentage of .99104.

Q.: Who was the author of “Moneyball”?

A.: Michael Lewis