clock menu more-arrow no yes mobile

Filed under:

Sabermetrics 101: Evaluating Fielding

Baseball can be split into two major areas: offense and defense.  And defense is split into pitching and fielding.  We've had a good idea of what makes a good batter or a good pitcher for a while now.

But when we say a player is good fielder what exactly do we mean?  What are the different skills that we're trying to measure?

Well, it's going to vary by position of course.  A shortstop needs a stronger arm than a second baseman, unless the shortstop is David Eckstein. But in general, we can probably break fielding down into the following skills:

  • Positioning
  • Range
  • Hands
  • Arm

Some of these can be expanded even more, but these four items make a pretty good starting point. Let's look a little deeper at each one.


Ever pay attention to the outfielders between pitches?  If not, you might be missing the crucial reason why a screaming line drive turns into just another out.

Fielders tailor their starting locations based on the particulars of the situation.  Some of the more apparent ways include the infield shift, or a no double defense, but oftentimes moving just a few steps can make a tremendous difference.

For a variety of reasons, positioning is often overlooked when evaluating a player. 

First, it's tough to identify good positioning - both before and after the fact.  Where the players are located before the pitch is rarely shown on television, and even in person, it's often hard to scan the entire field. 

We also aren't always aware of what the proper positioning should be for a given situation.  We might know that given hitter pulls the ball a lot, but does that mean the center fielder should shade two steps to his right, or five?  How likely is a batter to hit the ball to a given location anyway?

Finally, good positioning makes a play look routine.  If a player is already in the vicinity of the ball, then he doesn't need to work as hard to get there.  Unconsciously, or perhaps consciously, we don't give the fielder as much credit as if he raced across the gap and made a diving grab.

Should we?  To whom do we give credit for the proper positioning?  Much of the time, the coaching staff is responsible for moving the players around.  If the coaches handle the positioning, should it even be included in our player ratings?

I can't answer whether it should be or not, but right now, it is. 

Because positioning is not currently being tracked, we can't determine whether a play is made due to good positioning or good range.  We'll talk more about this in part two, when we look at the different evaluation systems throughout history.


Range generally reflects how much ground a fielder is able to cover in order to make a play.  When you see Carlos Beltran run down a ball in the gap, that's indicative of good range.  When you see Derek Jeter take two steps to his left and dive, that's not very good range.

Range itself can be considered the sum of three overlapping skills: reaction time, reading the ball off the bat and speed.

Reaction time represents how quickly a fielder reacts to the hit ball.  Obviously quicker is better than slower, but a good reaction time is more important at certain positions than others.  A third baseman needs an extremely quick reaction if he's going to spear the line drive down the line.  A left fielder might not need to respond as quickly since most of the hits in his direction are fly balls. 

Being quick to react doesn't do a whole lot of good if you start moving in the wrong direction.  Many an outfielder has reacted immediately to a batted ball by taking a step in, only to watch the ball soar over his head (it happened to Ryan Braun on Saturday night). 

Outfielders generally have a more difficult job of reading the ball.  In the infield, you have to deal with three variables, how hard the ball was hit, the angle of the ball (was it hit to your left or right and how far), and the bounces.  Granted, the bounces can be predictable, but it's fairly easy to make a determination where the ball is going to end up.

If the ball is hit in the air, a bunch of additional variables are introduced.  Besides needing to figure out how hard the ball was hit and which direction to move, you need to consider the vertical angle - is it a high fly ball, a low line drive, something in between - , whether the ball is curving and, if so, is it slicing or hooking, and even the wind currents.

Deciding where the ball is going to end up based on all that information can be a very difficult task.  And it all needs to be considered in enough time to actually make the play. 

That's where speed comes into play.  Being fast can make up for a poor reaction time, or difficulty reading the ball off the bat.  If you combine speed with good reactions, and good instincts about where the ball is going to drop, that's how you get a Carlos Beltran or a Willie Mays.

Fans sometimes overlook good range because it's not flashy, just like good positioning.  A player who breaks late on a ball but makes a diving grab looks more impressive than a player who easily glides to the ball and gets there with plenty of time.  But the second player is the one exhibiting more range, and is likely the better fielder.


Having good hands is much more important in the infield than in the outfield.  In the outfield, the game is simple.  The batter hits the ball, you catch the ball.  In the infield, however, you have to deal with a lot more variety, which puts an added burden on the fielder.  Screaming liners, slow rollers, bad hops.  Even if the infielder can get a glove on the ball, he needs to grab it, transition to his throwing hand and get the ball to first base to beat a speedy runner (or a Molina brother).

Hands measure the fielder's capability to hold onto the ball once he gets it, to avoid bobbles, and to get the ball out of his glove and over to the first basemen.

It easy to see an examples of bad hands.  We've all seen a second baseman who gets in front of the ball and just boots it.  Or the third baseman who gets eaten alive by a hard hit grounder.

Good hands are a lot harder to see.  For a player with good hands, there's a smoothness to their game - almost a gracefulness.  Omar Vizquel, while not as great a fielder as he's portrayed in the media, has good hands. 

In general though, we measure good hands by the absence of bad hands.  We'll cover this more in part two as well


A good arm is responsible for perhaps the most impressive plays on the field.  We all remember Ichiro gunning down Terence Long at third base in 2001.  Going back a little further, Roberto Clemente's arm in right field was legendary.

Correspondingly, a bad arm is responsible for some of the most embarrassing plays.  Johnny Damon's noodle arm is a punchline in sabermetric circles.  And we all cringed when Chuck Knoblauch lost the ability to make the short throw from second base (or maybe it was just us Yankees fans).

Two distinct concepts are wrapped up in arm; strength and accuracy.

Having a strong arm means nothing without accuracy.  Shawon Dunston had perhaps the strongest arm ever for a shortstop, but he rarely had any idea where the ball was going.  Vladimir Guerrero was the same way in right field.  While he occasionally nailed a runner at the plate, he more frequently airmailed the ball over the head of the catcher (and sometimes the pitcher).

But strength we can see, and so that's what we remember.  We can name Jesse Barfield as the strongest arm of the eighties, but can we name who had the most accurate arm?

I have no idea who it might be, but accuracy wins a lot more games than strength does.  For infielders especially, being accurate with your throws to first base can make a tremendous difference.  Poor accuracy can be overcome to some extent by a good first baseman - one who can dig balls out of the dirt (i.e. not Jason Giambi).  From an evaluation perspective, that makes things harder for us, but with the right level of data we can overcome the difficulty.


We've looked at the different components of fielding, and described them in some detail.  We've also identified some of the difficulties in isolating and measuring each of the components.  We'll cover this topic in more detail in part two of this series, where we look at the different fielding metrics, from the Fan's Scouting Report to TotalZone to UZR, and everything in between.