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Baseball’s data revolution is elevating defensive dynamos

When the Tampa Bay Rays gave outfielder Kevin Kiermaier a six-year, $53.5 million contract extension last month, they were not rewarding him so much for his prowess at the plate. He is a career .258 hitter who hits few home runs.

What most compelled the Rays to hang on to Kiermaier was his ability to field his position. Kiermaier, hardly a household name in professional sports, represents the new order in baseball, a sport that has been reshaped in staggering ways in recent years by a convergence of statistical analysis and camera technology.

There’s a newfound appreciation for players who do their best work with their gloves, not their bats.

“We’re looking at it in terms of one of our core players, and what he means to us,” said Chaim Bloom, the Rays’ senior vice president for baseball operations. “But we do see around the league, more and more, teams are taking note of a variety of skills, and trying to evaluate all the things players bring to the table as accurately as they can.”

He added: “And defense is certainly one of those things.”

It has not always been so. Until recently, baseball executives might have thought they knew good defense when they saw it, but they had little data to work with. Willie Mays, Ozzie Smith and Brooks Robinson — all stellar in the field — played long before the arrival of advanced statistics like Defensive Runs Saved and Ultimate Zone Rating.

Statcast, Major League Baseball Advanced Media’s proprietary combination of radar and optical tracking technologies, has been heralded as a data revolution. Statcast’s cameras have captured volumes of hitting, pitching and baserunning data in ballparks throughout the league since 2015.

Last season, the technology expanded to measure outfielders’ defensive aptitude, including a defender’s arm strength, first step, route efficiency and reaction time.

Daren Willman, the director of baseball research and development for Major League Baseball Advanced Media, known as BAM, said last year that he was confident about Statcast’s data and its potential effect on players’ values.

“Where it’s really going to end up is, players are going to start getting paid a ton more money because they play great defense and everybody realizes it,” Willman said in an interview with The New York Times Magazine.

Willman’s sentiments seemed validated when Kiermaier, widely regarded as a defensive whiz, signed the extension with the Rays.

According to Defensive Runs Saved and Ultimate Zone Rating, Kiermaier’s glove has been the most valuable in baseball since 2014.

Statcast’s data further illuminated his fielding prowess with something called Catch Probability. Weighed on a 0-to-100 scale of difficulty, the new statistic measures the rate at which outfielders catch fly balls. Last season, BAM calculated, Kiermaier caught 17 of 26 balls (65 percent) that had a leaguewide Catch Probability of 0 to 50 percent.

“That means he made 17 exceptional catches,” Willman said in a recent telephone interview. “You’re at liberty to take it as you will, but based off our metrics, those are 17 outstanding plays.”

BAM, a company owned jointly by all 30 major league franchises, disseminates its Statcast data equally to every team. What individual teams do with the information is their business. Some front offices, like the Rays, have begun to integrate the research into the value of game-saving defenders like Kiermaier.

“We’ve always tried to evaluate defense and really everything that goes on on the field as precisely as we can,” Bloom said. “And having Statcast available to us, even though it’s in its infancy, and we’re learning about it, makes a more precise evaluation possible.”

In terms of FanGraphs’ Wins Above Replacement, Kiermaier has been worth about as much as the undisputed stars Yoenis Cespedes, Andrew McCutchen, Robinson Cano and Joey Votto since entering the league three seasons ago. Unlike these players, Kiermaier does not hit home runs or get on base consistently enough to be held in the same regard by most fans.

Regardless, the Rays believe Kiermaier, a 31st-round draft pick in 2010, is a unique talent, one who deserves a star’s reward.

Bloom said that Statcast’s data on Kiermaier “backs up what we’ve known for a while.”

“Especially when Kevin got to the upper levels of the minor leagues, and came close to breaking into the big leagues, we knew that we had a very special athlete and player on our hands,” Bloom added. “That made it a lot easier to target Kevin as someone that we wanted to commit to.”

Despite the advances, defense remains hard to measure and hard to understand. The Washington Nationals paid a big price in their trade for Adam Eaton, and the Chicago Cubs grossly overpaid for Jason Heyward. Both those players, like Kiermaier, derive their value mainly from their youth and defense.

Defense, in contrast to power and the ability to draw a walk, declines progressively with age.

“The skill that will fall off first is speed,” said Jeff Zimmerman, a statistician and writer for the website FanGraphs, “and if that’s a major component of a player’s defense, that will fall off quickly too.”

Zimmerman found that 29-year-old center fielders saved about four fewer runs on average per season than those a year younger, according to Ultimate Zone Rating. And they deteriorate further from there.

Kiermaier’s skills are so unusual, however, that barring a major injury, his defense should remain superior into his 30s. “Even if he loses a step, he could still be really good,” Zimmerman said. “And that’s still a valuable player.”

Bloom was hesitant to call the eight-figure extension a watershed moment for baseball. But for a team that spent just $67 million in total payroll in 2016, he acknowledged, “It might be for us.”

Kiermaier’s big payday could still change the way others evaluate players, and how they attempt to use Statcast to turn rows of numbers into tangible dollar values, ones that turn relatively unknown players into multimillionaires.

Beyond extensions and free-agent contracts, Statcast could ultimately have a greater impact on arbitration cases. Arbitration, the process by which players with at least three full seasons of major league service time but fewer than six earn moderate salary raises, has been slow to incorporate the new evaluation metrics. Players who excel in more traditional categories, like home runs and wins, tend to be the ones paid handsomely; defense falls by the wayside.

“There’s so many different things that go into the arbitration process, and I think players and clubs all acknowledge that it’s an imperfect process,” Bloom said. “I think the process has evolved over the years, to value different things, so it wouldn’t shock me if it evolved again.”

In the meantime, the defense revolution is blossoming one contract at a time. And the Rays and Kiermaier are, perhaps, the face of it.

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