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Two games, two identical ground balls by the same batter. Why does one become a dazzling double play and the other a clutch hit? An exclusive look at a cutting-edge motion tracking system being developed by MLB Advanced Media shows all—including a glimpse of the game's data-driven future

WITH A RUNNER on first in the top of the fifth inning at Citi Field on April 21, Cardinals centerfielder Jon Jay hit a hard ground ball up the middle, just to the left of second base. In the fourth inning the next night, with the bases loaded, Jay did the same thing: ground ball, up the middle, just to the left of second. The first was snagged by diving Mets shortstop Ruben Tejada, who started a slick 6-4-3 double play—a key moment in New York's 2--0 win. The second sneaked by diving shortstop Omar Quintanilla and became a two-run single that broke a scoreless tie and proved to be decisive in a 3--0 St. Louis victory.

Until now, fans and teams alike could only speculate as to why two seemingly similar plays led to such different outcomes. MLB Advanced Media (MLBAM) is about to change all that. This season MLB's digital technology division is testing a new camera-and-radar-based system in three ballparks—Citi Field in New York City, Miller Field in Milwaukee and Target Field in Minneapolis—that measures and tracks with extreme precision almost every movement players make: their exact positioning, how fast they run, how quickly they field and release balls, how hard they hit and throw them, the lengths of their leads and the efficiency of the paths fielders take to fly balls. Bob Bowman, the president and CEO of MLBAM, expects to have the system up and running in all 30 stadiums by Opening Day 2015.

The system will be invaluable to teams, which will use the vast data to critique their own players and strategize for opponents. It will also provide a new level of insight and entertainment for fans. MLBAM plans for the tracking data to be available almost instantaneously so it can be used in broadcasts just as replays are now. How fast did Billy Hamilton get down the first base line? Does Andrelton Simmons have the strongest arm at shortstop? What kind of jump does Jacoby Ellsbury get on fly balls in the gap? Now we will know.

The data will also expose the nuances in seemingly routine events, like Jay's grounders. "To the naked eye, it looks like they're about the same play," says Bowman. "When you break it down, you find that everything was different." MLBAM provided SI with the proprietary data it collected for those two plays to demonstrate the tracking system's capabilities—and show how slim the difference between a double play and a two-RBI base hit can be. "Baseball is a game of inches," Bowman says. "Now we're going to know if it's one inch, or three."


[The following text appears within a diagram. Please see hardcopy or PDF for actual diagram.]



On most teams the shortstop is in charge of making slight adjustments to infielder positioning, but the Mets entrust the job to 29-year-old second baseman Daniel Murphy. "Murph's a little bit more of a veteran, has a little more information," says manager Terry Collins. In fact, Murphy had a lot of information on Jay, against whom Murphy played in college—Murphy at Jacksonville, Jay at Miami. ¬∂ On April 21, the lefthanded-hitting Jay was ahead of righthander Jenrry Mejia in the count 2 and 1, with no outs and Jhonny Peralta on first. But the following night, with the bases loaded and nobody out in the fourth, Jay was behind 0 and 2 against righty Dillon Gee. "Two strikes, [Jay] likes to go the other way," says Murphy, who positioned his shortstops accordingly. ¬∂ On the first at bat Tejada stood 27 feet, 9.65 inches to the left of second base. But for the second Quintanilla was more than three feet closer to the third base hole: 31 feet, 0.34 inches from the bag. "Jay had just fouled a ball almost over [the third base] dugout earlier in the at bat, and as soon as he did that, I moved Quintanilla over another step," Murphy says. Those three extra feet would make a very big difference.




Mejia's 2-and-1 pitch, a cutter, came in at 91.4 mph, with a spin rate of 2,193.34 rpm. Gee's 0-and-2 offering was a curveball at 74.7 mph, spinning 2,289.78 rpm. Jay hit both grounders to nearly the same spot, just to the left of second base, but, perhaps because the pitch had more velocity, he made harder contact on the first night: that ball came off his bat at 102.16 mph, compared with 94.18 mph a day later. Still, Tejada reacted more quickly than Quintanilla did. It took Tejada just 0.15 of a second to make his first step toward the ball. Quintanilla needed more than twice that, 0.32 of a second. There are several reasons why Quintanilla might have been slower to react. It was raining at Citi on April 22, making it harder to see. And Collins theorizes that Jay's bat may have been a factor: Some players have trouble picking up a white ball off blond-tinted wood.




As the ball skittered up the middle, both Tejada and Quintanilla hustled to their left and dived. On the first play Tejada covered 16 feet, 7.36 inches of ground: Given his initial positioning and his quick reaction time, that was enough for him to get his glove on the ball. But remember how Quintanilla, at Murphy's urging, had moved closer to the third base hole? His dive for Jay's grounder came up short by 3 feet, 7.59 inches—though, since the tracking system measured from his center of mass and not from his outstretched glove, in truth he missed making the play by much less than that.



Once Tejada had the ball in his glove, he knew he had to work quickly for the Mets to turn a DP. He did: From a prone position, he required just 0.87 of a second to make a backhand flip to Murphy, who had just reached second base. "It was a perfect feed," says Murphy. The second baseman knew he'd easily get the force-out on Peralta; the slow-footed Cardinals shortstop started the play with a lead of just 10 feet, 4.08 inches off first and reached a maximum speed of 15.87 mph on his way to second. But Murphy knew that if he caught Tejada's feed in his glove, he wouldn't transfer the ball to his throwing hand and relay to first in time to beat the speedy Jay. So he barehanded it, catching and releasing the ball in just 0.55 of a second. His throw to first had a velocity of 66.88 mph."[If] I set my feet, I'd hope I throw a little bit harder than that," Murphy says. Still, it was just hard enough to get Jay, who flew down the first base line at a max speed of 18.65 mph. He was out by 1 foot, 9.4 inches. "It was a big play in the game," Murphy says. "It would have been first and third with no outs, and instead it was a double play and we could get out of the inning."



The next night would bring no such result: Jay's single drove in two runs and keyed the St. Louis win. This time Jay could coast down the first base line—his max speed was 16.8 mph, meaning that he was outrun by lumbering first baseman Matt Adams, who reached 17.87 mph as he scored from second. Chris young's throw from center was cut off, and Murphy and Quintanilla were left wondering if they had outthought themselves. "I looked at Q, and he was a little bit frustrated, because I think he would have stayed where he was if I hadn't moved him," Murphy says. "You take all the information you have, and sometimes you get beat."


Get an exclusive look at how MLB's tracking technology system will enhance game broadcasts: Watch data-enhanced clips of Jon Jay's mirror-image ground balls against the Mets at


Photograph by Kathy Willens/AP

APRIL 21 Tejada dived ... and nabbed Jay's grounder, then made a flip to turn two.



APRIL 22 Quintanilla dived ... but Jay's grounder up the middle got by him for a two-run single.