ST. LOUIS -- Andrelton Simmons' eyes tell him everything. He stands where the infield dirt meets the outfield grass. He prepares, knowing where each batter tends to hit the ball. He anticipates where the swing and the pitch will intersect, yet he says his fielding precision at shortstop comes down to one thing: what he sees when the ball hits the bat.

First, Simmons said, he observes direction. Is it a ball he has to go in to get? Or does he have to go back and away from the cut of the grass?

"You anticipate it, but you can't really predict where [the ball] is going to go because some guys are just quick with their swing," the Atlanta Braves shortstop said before a game in St. Louis. "Some guys might get jammed. You've got to see it. He might be trying to pull, but the pitcher might have thrown the ball where he didn't want it to go."

It is in there, those moments when a pitcher does not have his best stuff on the mound, where the Braves really see Simmons' impact on the field.

"A guy just so happens to get jammed a little and he hits the ball up the middle, and there's Simmons; smack, he's out," Braves manager Fredi Gonzalez said. "A different shortstop, the ball goes through."

Fielding is the one aspect of baseball where our eyes convey a different story to everyone. Where someone sees good range, another will perceive better positioning. Where one evaluator notices reaction time, another observes slower velocity off the bat. One fielder might think he needs to go back, another will see he has time to let the ball come to him.

Looking at the numbers, they leave room to debate the best fielders, too. Take defensive runs saved (DRS). Jason Heyward rates the highest in the majors with 25 DRS this season. But use ultimate zone rating (UZR) and the Kansas City Royals' Alex Gordon leads the majors at 23.7 -- with Heyward second.

Gonzalez said he listens to everything he can about advanced statistics. The stat packet he receives is about two inches thick, and as he flips through it each day he'll usually find a magic number to help with the game matchups. Some days, though, there are no numbers to help him prepare for the game.

"It's like, well, nobody gets to play today," Gonzalez joked. "By these numbers we should all just go ahead and go home."

Some advanced stats are just not helpful. Because, as Gonzalez put it, "At the end of the day you go, well, what can we do with this?"

Yet, while it's impossible to evaluate fielding precisely, the ability to field the ball has never been more important than it is today. Runs are more difficult to come by, and in close division races in the second half of the season -- such as the National League East, Central and West -- defense could decide the division champion.

"It's ultimately important," Gonzalez said about the impact fielding has had on the NL East and the Braves' ability to win games this year. "There's four aspects of our game: pitching, hitting, baserunning and defense. You can live without the hitting, you can live with a team kind of struggling, but you can't live without pitching, and you can't live with shoddy defense. You just can't. It's impossible."

San Francisco Giants manager Bruce Bochy agreed.

"To me, defense and pitching, they go hand in hand," Bochy said. "That's been a big reason our pitching has done such a good job. Our defense has been on [its] toes."

Baseball people hear this often, Braves right-hander David Carpenter said. "Offense wins games, pitching and defense wins championships. We are trying to do that here."

But, Carpenter has discovered, good fielding also impacts his ability to pitch well.

"It's a big confidence booster knowing that you don't have to be out there and be perfect," said Carpenter, currently on the 15-day disabled list. "There's not as much stress put on every single pitch because you know if they make contact the guys are busting their butt to go get the ball for you."

Having good fielders also helps the catcher.

"It always helps that you know plus defenders are out there," Braves catcher Ryan Doumit said. "It makes it that much easier as far as pitch selection."

Currently, teams do not have good data to evaluate fielding. While some advanced stats do not transfer well for use on the field, player tracking -- when it becomes available to teams -- is the next and new way teams can gain an advantage over other teams.

From every advanced stat or system he has seen so far, Gonzalez is most excited about being able to use player tracking and, ultimately, improve defense.

"It's unbelievable," Gonzalez said of FIELDf/x and Major League Baseball Advanced Media's (MLBAM) statcast player tracking. "It has the angle of the ball, how long it stayed up in the air. It shows the outfielder -- which route did he take? Did he go back, or did he go [to the right] and come back?"

This season, there are two systems being tested by MLBAM. They will soon decide whether to integrate the two together or chose one over the other.

FIELDf/x is currently installed in five major league ballparks.

"FIELDf/x is a camera-based tracking system that tracks all of the movement of the players, the ball off the bat and the throws. So all of that, and the player events in a given play," said Mike Jakob, president and chief operating officer for Sportvision, Inc. "It's a four-camera system. It's a project we've been working on in conjunction with MLBAM for several years."

MLBAM statcast player tracking is currently installed in three ballparks and it will be in all 30 by 2015. MLBAM foresees the data rolling out in a similar fashion as PITCHf/x did. So they will work closely with the clubs to ensure the data is authentic, accurate and in real time. Then the clubs will get a daily pipeline to the raw data that is pushed to them every night.

Until now, very few people have talked specifically about how this system could transfer to the field and ultimately -- and most importantly -- help managers. Sure, fans will enjoy it, but will managers use it?

"From all the ones that have come out, [player tracking] is the one I really got excited about," Gonzalez said. "Because you could actually go to the player and say, 'We've got to work on your jumps, because this ball was up four seconds, and instead of you going directly to the ball, you kind of went back and then came over.' So you can use that as a teaching tool.

"The other [stats], when I first figured out OPS and I fully had a good grasp of it, they went to a different level with it -- X WAR, or more weighted, [or something]," Gonzalez said laughing. "I'm like, 'Oh my God, I just figured out OPS.' I still haven't figured out ERA."

Many players, coaches and managers are wary of how to incorporate advanced stats into the game.

"They talk about all the defensive metrics on TV," Giants shortstop Brandon Crawford said. "But I think just watching a guy and seeing how he fields the ball -- you know, how strong his arm is -- stuff like that, I think an eye test will tell you if a guy is a good fielder or not."

However, Simmons, much like his manager, said he does pay attention to advanced statistics.

"I try," Simmons said. "I'm slowly getting the hang of it. Yeah, I'm trying to learn more and more every day."

As they work on a way to evaluate fielding, Simmons said he hopes the people interpreting the data understand each position and understand how hard it is to play defense.

"Obviously, you have to judge plays that would have normally been made," Simmons said. "Like errors, I don't think much of errors, because a guy that gets to everything, he's more vulnerable to make an error, because he went to the hole and got the ball deep. Sometimes you overdo it, or you throw a ball and give a guy an extra base, and I can see those things [as errors]."

Simmons, of course, doesn't have a lot of time each day. Baseball is a demanding sport. What motivates him to learn about sabermetrics?

"You want to compare yourself to how other players do," said Simmons. "If you notice another good shortstop, you want to know, oh, he does this better. Then, you might go looking at video and see why he does this better, stuff like that. You want to compare yourself and see where you're at."

Who would he compare himself to?

"Hmm, I don't know," answered Simmons after he thought about it for a while.

What about Troy Tulowitzki?

"I see him every once in a while in the highlights," Simmons said. "I try to look at some of the stuff and see, oh, I would have made it this way. Everybody plays defense a little differently. I try to see, he makes this play good, or I can do this. I learn from everybody pretty much."

It is in this, the fielder's desire to learn how he can see more clearly, where one can always, with or without player tracking, define the best fielders. With player tracking, the game then becomes a matter of how teams use the data to give them an advantage.

Finding the secrets to a different edge or a new approach, that's baseball today. At some point, though, even fielding data will run its course, and teams will look for something else.

"The next one will be MANAGERf/x," Gonzalez joked. "'Fredi, we've got to get you wired to the monitor and see when you put a squeeze on, and we'll see how much of a ba bum, ba bum, your [heart] goes,' or when you bring that lefty in and you go, 'Oh s---, is he going to get somebody out?' Ba bum, ba bum, ba bum."

Anna McDonald is a regular contributor to the SweetSpot blog.