As each opposing batter steps to the plate, you might notice New York Yankees outfielder Brett Gardner do something you would not expect: He often removes and repositions his cap as if to adjust it, a curious move for a player who shaves his head almost daily.

So does Jacoby Ellsbury, who has a full head of hair, and so does Aaron Hicks, who like Gardner, has taken a blade to complete the job that Mother Nature started.

But Gardner is not repositioning that cap for comfort, or checking to see if his long-departed hair has miraculously returned.

"Everyone notices the infield shifts because you've got guys playing completely out of position. But what people don't realize is that we're doing a lot of similar things in the outfield, too, these days. It may not look as radical, but we've been doing it for the last year, year-and-a-half now."

He, like the others, is checking to be sure he is standing where he is supposed to be standing -- a hidden aspect of big league defense that goes beyond the infield and is finally getting some of the spotlight.

When it comes to positioning their outfielders, the Yankees literally keep the information under their hats. Before each game, bench coach Rob Thomson, responsible for the outfield defense, gives Gardner, center fielder Ellsbury, right fielder Hicks and rookie outfielder Aaron Judge an index card with precise locations for each opposing hitter.

Those locations are determined by a proprietary computer program developed by the Yankees' analytic squad, headed by David Grabiner. It takes a multitude of factors -- among them the hitter's power, his tendency to pull or not pull the ball, and his career history against the Yankees' pitcher that night -- and spits out a spray chart which places the outfielder in the optimal position to make a play.

"We have analytical assessments that show specifically where guys hit the ball," a Yankees staffer told ESPN.com. "I mean, it shows us exactly where guys hit the ball just about every time. And it's hitter/pitcher specific, based on pitch velocity and location. Positioning is based on a lot of factors, including the speed of the defender."

Those positions are notated as plus or minus numbers, in feet, from the "default" position the Yankees' coaching staff plots out on the field. There are numbers for the depth at which the outfielder should be playing, and how far he should shade to the right or left. For example, for a strong right-handed hitter such as the Baltimore Orioles' Mark Trumbo, the card might read "+15" for distance and "+10" for side-to-side positioning, indicating the player should play 15 feet deeper than the default position and 10 feet closer to the line.

The graphic above illustrates the default position for each Yankees outfielder, 30 feet from the wall on imaginary lines drawn across the bases. The team has devised a plus/minus system to determine position shifts for various opposing hitters. ESPN

"Everyone notices the infield shifts, because you've got guys playing completely out of position," Gardner said. "But what people don't realize is that we're doing a lot of similar things in the outfield, too, these days. It may not look as radical, but we've been doing it for the last year, year-and-a-half now."

Over the past decade, infield shifts, once thought to be a novelty indulged in by "eccentrics" like Chicago Cubs manager Joe Maddon, have become as commonplace as the strikeout. Five years ago, teams employed 2,464 shifts; this year, it's projected to be 28,117 -- a number high enough that MLB is now looking into a series of rule changes, including restricting shifts. Since 2006, the number of runs scored in Major League Baseball has plummeted from 23,599 to 19,761, and among the insiders ESPN.com spoke to for this story, there is the belief that it is partly due to base hits being taken away by the shift. In fact, one Yankees executive predicted baseball would never see another .400 hitter because of the shift.

Outfield positioning, on the other hand, is often overlooked. That is, until early June, when it was revealed that the Los Angeles Dodgers had requested, and been refused, permission by the New York Mets to position their outfielders with the help of laser range finders, and to mark those positions on the outfield grass with spray paint. In the wake of that story, it's becoming more evident that outfield shifting is perhaps just as complicated and as crucial as it is in the infield -- and lately it has been pushing the boundaries of baseball.

It's far from science fiction

Using a laser to locate the depth of outfielders may seem extreme -- the Yankees, for example, have pinpointed their default position as 30 feet in from the outfield wall in all fields without the help of a laser, merely the judgment of their fielders -- but there is really nothing all that radical about it. Although it may sound like something out of a science fiction movie, and raise the specter of a construction site, with tripods and laser levels set up all over the field, the reality is a lot simpler.

Teams that use lasers to position their outfielders -- and while the practice is not commonplace, MLB executives say the Dodgers are by no means alone in using them, listing the Texas Rangers as another example (the Yankees, too, have used lasers to determine the distance to the outfield walls at their spring training complex in Tampa) -- generally use the type of handheld range finders used by golfers to measure the length of their tee shots, which usually sell for less than $200.

There are even apps available for as little as 99 cents, although their accuracy and ease of use can't compare to the higher-priced models. But whatever type a team chooses to use, the procedure is the same: The device is held by hand by a team staffer from behind home plate during batting practice and aimed at a player standing in the outfield. The staffer keeps moving the player until he is standing in the position the team wants, at which point he either must remember that precise location or, as the Dodgers requested, mark the spot in some way in the outfield.

That is where the Mets' objections came in. They asked for a ruling from MLB, which announced that deliberately marking the field was a violation of league rules.

"Technically, you're not allowed to purposely damage the field in any way," a league executive told ESPN.com. "That includes spray paint, or leaving golf tees in the outfield, or even kicking a divot into the grass with your heel."

The executive admitted, however, that it was difficult to enforce such a rule when it is routine for pitchers to dig up the area around the rubber with their spikes and for hitters to "groom" the batter's box before each at-bat. He also acknowledged that the Dodgers were probably not the only team to use laser technology to position outfielders, and that there was nothing in the rulebook prohibiting a team from using them before the game, either at home or in a visiting park.

And according to Dodgers manager Dave Roberts, other teams had asked for, and been granted, permission to mark the outfield in Dodger Stadium.

"Every team has different priorities," Roberts said at the time. "There have been various teams that have asked to make a mark on our field. We've been OK with it."

A baseball source with knowledge of the Dodgers' position methods told ESPN.com the original request -- to use the laser to pinpoint a spot and mark it with an easily-removable shot of spray paint -- was approved by Citi Field's groundskeepers. It was then vetoed by Mets manager Terry Collins.

According to Dodgers manager Dave Roberts, teams have asked for and been granted permission to mark the outfield in Dodger Stadium for the purpose of positioning. Jayne Kamin-Oncea/USA TODAY Sports

"It's not that big a deal, but TC totally overreacted to the whole thing," the source said. "Ninety percent of the time we've asked, the other team was OK with it, and [the Dodgers] have allowed other teams to do the same."

Mets GM Sandy Alderson said the Dodgers did not ask permission.

"We observed some members of the Dodgers organization using technology to establish defensive positions, presumably to use during the game," Alderson said at a news conference. "We weren't sure that was appropriate."

MLB's objection to the use of laser range finders during the game is an extension of its policy disallowing electronics of any kind in the dugouts during a game -- a rule designed to prevent sign stealing.

Of course, the most famous example of sign stealing in baseball history was decidedly low-tech, when New York Giants catcher Sal Yvars revealed that, by using a telescope mounted in the center-field bleachers at the Polo Grounds, Bobby Thomson was tipped off that Ralph Branca was about to throw him a fastball in the rubber game of a 1951 playoff series with the Brooklyn Dodgers. Thomson subsequently hit the "Shot Heard 'Round the World," propelling the Giants to the World Series.

Recently, baseball relaxed that rule to allow managers the use of Wi-Fi-disabled computer tablets preloaded with statistical information, spray chart, and video of previously-recorded at-bats between hitters and pitchers playing in that night's game.

But allowing NFL-type espionage from the owner's box, including aerial photographs, wireless communications between coaches in the stands and on the field, and photos faxed to the sideline, isn't coming to baseball anytime soon.

"We observed some members of the Dodgers organization using technology to establish defensive positions, presumably to use during the game. We weren't sure that was appropriate."

"Baseball has been kind of slow to adopt that kind of technology," Yankees GM Brian Cashman said. "Look at how long it took to get replay."

As a result, outfield positioning, in spite of the sophisticated computer algorithms designed to pinpoint them with precision, is often as low-tech as a coach simply waving a player over from the dugout, the way it's done in Little League or in Sunday morning softball games across the country.

It is customary in a visiting park for a coach to walk the field with the team's analytics expert before a game to map out outfield positions, but once the game starts, it often comes down to educated guesswork.

"Outfield positioning has always lagged behind infield positioning," Mets assistant GM John Ricco said. "Industrywide, this is still kind of a work in progress."

Landmarks, lines of sight and other low-tech approaches

The Yankees take a simple approach to determining the "straight-up" position for their outfielders. Thomson merely draws a visual straight line from first base through second base and all the way to the outfield wall to determine the default position for his left fielder, and a line from third base through second base for his right fielder. The center fielder playing straightaway stands on the axis of a line drawn between home plate, second base and the center-field fence. All position themselves 30 feet straight in from the wall as a starting point.

From that starting point, the outfielders tip their caps to consult the cards that pinpoint the precise location for each opposing hitter.

To ensure his fielders are in the right spot, Thomson said he sits in exactly the same seat in the Yankees' dugout every night, from where he can see the players in relation to reference points on the outfield wall. In left field, his reference point is the first "S" in the first State Farm sign; in right, it's the "P" in Pepsi. Center is the "4" in the 408-foot marker. In a visiting park, Thomson uses the same system, choosing a spot in the dugout from which he can see the reference points he determined from his pregame walk-through in the outfield.

Want to know where Brett Gardner and the Yankees' outfielders are going to position themselves for a particular hitter? Check under their hats -- or the ads on the outfield walls. AP Photo/Kathy Willens

But Thomson admits it is difficult to tell if a player is in precisely the right spot from the vantage point of a dugout, especially regarding depth.

And many other factors can cause an outfielder to have to adjust his position significantly from where the computer has told him to play. That's because outfielders must be able to see the hitting zone, and that view is often obstructed. Part of that is due to the infield shifts, which often cause an infielder to move into an outfielder's line of sight. Part of it is due to umpires, who also must shift their positions when the infielders shift. Sometimes, the position of the sun or the looming of shadows can force an outfielder to move.

"We try to be exact out there, but you've still got to read swings," Gardner said. "And to do that, sometimes you can't stay in the middle. I have to decide whether to choose the left fork in the road or the right fork in the road. So you might not be standing exactly where the computer tells you to."

Still, Gardner said, "When you're trying to cover 2½ acres of ground [the size of the Yankee Stadium outfield], I don't think 10 or 15 feet makes that much of a difference."

"If our pitcher makes a mistake, all that other stuff goes out the window."

Others in the organization, however, might beg to differ. "Our infield shifts do very well, but our outfield positioning is a problem," a Yankees staffer said. "It does not match up with the recommendations."

The Yankees say they are "plus-30" with infield shifts, meaning they have converted 30 balls in play into outs that would have been hits with a conventional infield alignment. They say their shifts are especially effective when Masahiro Tanaka is pitching, because the consistency of the location of his pitches within the strike zone makes it easier to position their infielders with precision.

Leaguewide, players are hitting .264 when not facing a shift, and just .232 against full shifts of three or more fielders on one side of the infield, according to ESPN Stats & Information. Against the Yankees, those numbers are .259 no-shift and .241 full-shift.

The Yankees' outfield positioning, however, is a different story.

The team's "out rate" -- the number of fly balls converted into outs by their outfielders -- has actually decreased since 2010, when they converted 69.2 percent -- a number that would put them second in the majors in 2016 -- according to ESPN Stats & Information.

But over the past five years, including the two seasons in which they have used their computer algorithm, the Yankees out rate has hovered at a decidedly middle-of-the-road 65 percent.

That can be due to several factors, including the age of the Yankees' primary starting outfielders, whose average age was 34.3 before Carlos Beltran was traded to Texas, and the effectiveness of their pitchers. The Yankees pitching staff's hard-hit rate -- on fly balls and outfield line drives -- this year is 34.6 percent, 23rd in baseball.

By contrast, the Cubs, with outfielders who average 26.5 years old and a staff with a hard-hit rate of 30.4 percent (fourth best in baseball), have converted 69.1 percent of their outfield chances which is second in the majors. The Kansas City Royals, with Alex Gordon in their outfield, lead the majors at 69.9 percent; the Tampa Bay Rays, with Kevin Kiermaier, are third at 68.4. The Dodgers, whose outfielders also average 26.5 years old, have converted just 66.6 percent -- 12th in baseball -- though, to be fair, their 30.3 percent hard-hit rate clips the Cubs for third best in the bigs.

So it is difficult to pinpoint exactly what determines the defensive efficiency of an outfield, but common sense tells you that precision positioning can't compensate for slow or aging outfielders or a poor pitching staff.

As Ricco said, "If our pitcher makes a mistake, all that other stuff goes out the window."