Baseball’s strike zone has expanded, and hitters aren’t happy

Few property disputes are so pitched as that over baseball’s strike zone.

The interpretation of what is and is not a strike frames the game like little else, defining the terms of the battle between pitchers and hitters. As such, it comes as little surprise that home plate umpires are subject to endless scrutiny, their interpretation of the strike zone for decades subject to shouts, insults, and epithets, with ejections more often coming from disputed ball and strike calls than any other realm.

Given the role of the strike zone in defining the game, it should come as little surprise the prized piece of real estate has garnered considerable attention at a time when run scoring is at its lowest levels in decades.

In 2014, the average team managed just 4.07 runs per game, down nearly 12 percent from its 2009 levels and the lowest average since 1981.

The potential factors are numerous: Attempts to eradicate performance-enhancing drugs, an influx of smoke-throwing arms with wipeout secondary pitches, more emphasis on elite defenders and shifts . . .

Yet there’s also baseball’s defining battleground, where the terms of engagement have changed.

“The bottom of the zone has dropped the diameter of a baseball over five seasons or so,” said Jon Roegele, who began examining the phenomenon for the Hardball Times in early 2014. “[Overall since 2009 the strike zone has] grown about 40 square inches. Pretty much all of the growth is happening at the bottom of the strike zone, at the knees.”

Roegele determined that the strike zone has expanded on average from about 435 square inches to about 475 square inches — an increase of roughly 9 percent — from 2009 through 2014, including a leap of 16 square inches from 2013 to 2014 alone.

The strike zone actually has narrowed horizontally, Roegele found, but called strikes are typically coming on pitches that are as much as 3 inches below where the bottom of the strike zone had been defined in 2009.

Major League Baseball officials — including commissioner Rob Manfred and VP of baseball operations Joe Torre, who is in charge of umpires — say uniformly that there has been no mandate to expand the strike zone. Still, Torre acknowledged that the current strike zone is larger than the one two years ago, while executives around the game have reached conclusions similar to Roegele’s over a multiyear period.

“It’s definitely shifted down,” said Yankees first baseman Mark Teixeira. “It’s gotten bigger and bigger the last few years.”

JOE MOORE, LUKE KNOX/GLOBE STAFF

The tendency to call pitches that are a full width of a baseball from the previous bottom of the zone is a game-changer in the most literal sense.

“If you swing at that pitch, you’ll ground it out or pop it up because you have to reach for it,” said Red Sox designated hitter David Ortiz. “I see it every night being called on everybody. That’s not a hittable pitch . . . No hitting coach teaches you to hit those pitches. There’s not any league — Little League to the big leagues — no one tells you to hit that pitch, because it’s not a strike. It’s crazy. The bottom line is it’s killing offense, especially with better pitchers now.”

What happened?

In 1996, baseball’s vertical strike zone had shrunk, often encompassing the area from slightly above the knees to roughly belt-high. Meanwhile, umpires displayed considerable variance in defining the horizontal strike zone, with some calling pitches well off the plate and others interpreting the plate more narrowly.

Discussions about the strike zone at the time focused A) on achieving uniformity and B) restoring the high strike. Few enforced the rulebook definition that was roughly at the bottom of a the letters on a player’s jersey.

Inside the commissioner’s office, at a time of exploding offense and pitching misery, an effort was made in the late 1990s, starting with the last formal change to the definition of a strike in 1996, to bring back the strike above the belt up to the bottom of the letters.

JOE MOORE, LUKE KNOX/GLOBE STAFF

But given that, in the American League especially (at a time when the umpires of the two leagues reported to different offices), the strike at the knees was infrequently called, the league also wanted to reinforce the location of the bottom of the zone.

That led to a redefinition of the bottom of the zone to the hollow of the knee, down from the prior definition at the top of the knees.

“No one thought the strike below the knees would start getting called,” acknowledged one person familiar with the conversations about the strike zone redefinition. “We just wanted to try to capture the strike at the knees.”

Everyone seemed unhappy with the adjustment — yet ire focused initially on the high strike and the diminishing outer edge of the plate.

“Guys were going insane,” said Red Sox bench coach Torey Lovullo, who last played in the big leagues in 1999. “I remember [barking] at the umpires all the time, ‘That’s not a strike. That’s up here at my chest.’ They’d say, ‘That’s the new thing. We’re calling that.’ ”

Pitchers such as Curt Schilling became irate at times about the inability to get strikes off the plate that umpires had called throughout his career. Umpires were furious with virtually every edict that came from Sandy Alderson, then the executive VP of baseball operations in the commissioner’s office, and distrustful of the 2001 introduction of the QuesTec evaluation system that graded umpire performances.

Yet over time, the friction dwindled. The switch from QuesTec to the Zone Evaluation system in 2009 offered umpires a better — and more welcomed — teaching method. Whereas QuesTec was in 11 parks in its last year, ZE was in all 30 parks. QuesTec had a lag of days before offering feedback; ZE allowed for reviews of every game on every night — with a technician manually framing the top and bottom of the zone on every pitch — and gave umpires both their scores and feedback the next day.

Not only could an ump get a grade quickly, he could also see, with video, if he’d had a consistent miss in calling, for instance, sliders away to lefthanded hitters or fastballs at the bottom of the strike zone.

The uniformity and accuracy of strikes made steady gains, a trend that several officials agree was aided by the changing demographics of the umpiring pool.

Of baseball’s current 76 full-time umpires, 20 were hired for the 2010 season or later, including 11 in the last two years. Eight umpires were added prior to the 2014 season with the growth of the umpiring staff from 68 to 74 due to the expansion of replay in 2014, while a new labor agreement between MLB and its umpires for the 2015 season added two more.

The result has been a huge influx of new umpires trained under the current strike zone using the new technological teaching tools, and calls from behind the plate that are closer to the letter of the law.

“We never had a mandate saying, ‘call the low pitch,’ ” said Mike Port, Major League Baseball’s VP of umpiring from 2005-11. “Our mandate was to call the strike zone.”

But that meant calling lower strikes. Technicians set the ZE system manually to define the bottom of the strike zone at the hollow of the knee at the stride point for every pitch. That’s where umpires are trained to call strikes, and they’ve responded. The result has been increased accuracy and uniformity.

Port said the scores of umpires went up every year he was in his position, finishing at about 94-95 percent for balls and strikes. Those grades have continued to rise over the last four years, to what one major league source estimated at an average of 95-96 percent, with nearly all umpires falling into the range of 92-97 percent accuracy – the low end of which would have represented the very best grades when QuesTec was first introduced in 2001.

“I think right now,” said one MLB official, “we’re probably calling the strike zone as accurately as we’ve ever called it.”

But an accurately called strike zone means, by rule, calling a pitch on which any part of the ball glides by the hollow of the knee while crossing any part of the plate. In this case, the improved accuracy has come at the expense of offense.

The impactIn the period in which Roegele found that the strike zone has expanded, offense has cratered. Last year’s 4.07 runs per game represented the game’s lowest offensive point since 1981.

Roegele estimates that the larger zone is responsible for about one-third of the offensive decline. Strikeouts per nine innings went up by about 10 percent from 2009-14, while walks per nine innings declined by roughly 20 percent.

Hitters are swinging at more pitches than they have in years, with a steady rise from swings at 45.2 percent of all pitches (excluding intentional balls) in 2009 to 47.2 percent of all pitches last season.

With pitchers well aware of the expanding lower zone, there’s been an increased willingness to attack a part of the strike zone where hitters are unable to drive the ball.

“There’s a difference in the strike zone,” said Cardinals catcher Yadier Molina. “That’s where you want to be as a catcher and pitcher — keep the ball down, and get as many ground balls as you can. That’s an advantage.”

In the area where Roegele has seen the growth of the strike zone, calls of ball four have plummeted. In 2009, the decisive pitch of at-bats to that band of the “expanded strike zone” resulted in a walk 9.7 percent of the time, slightly above the league average of 8.9. Hitters could take pitches around the hollow of the knee and head to first base.

No longer. In 2014, pitches to the “expanded strike zone” ended with ball four just 3.8 percent of the time, well below the league average walk rate of 7.6 percent.

In other words, batters are being forced to swing more than ever. Pitchers are smart enough to attack a region where they will get strike calls and contact will often produce ground ball outs and rarely yield a worse outcome than a single.

“You know the reason I’m still playing baseball? Because I learned what the strike zone was all about,” said Ortiz. “Now, all of a sudden, I go from being the one of the best hitters at recognizing the strike zone to being a guy swinging at everything. Why is that? Because you feel like when you’re walking to the plate, you’ve got two strikes. That needs to be fixed.”

Red Sox designated hitter David Ortiz was thrown out of the game by umpire John Tumpane after arguing a strike in April.USA Today Sports

A way forward?

There are different responses to the downward movement of the strike zone. Players like free-swinging Orioles slugger Adam Jones no longer have to apologize for an aggressive approach at the plate.

“I just go up there hacking. If it looks good out of the hand, I’m going to give it a whack,” Jones said.

Even a previously patient hitter such as Teixeira has embraced some of Jones’s mentality.

“I’ve had to be a little bit more aggressive. I’m still getting my walks, which is a positive, but it’s tougher,” said Teixeira. “Those low pitches you have to swing at are going to be ground balls. But I’ve adjusted and tried to just drive the ball more. Getting my home runs and my doubles and my walks is the only way to combat that.”

Low-ball hitters such as Mike Trout and Josh Donaldson have emerged as MVP-caliber players because their strengths align with the prevailing state of pitching.

Around the game, there are informal conversations about whether it might make sense for MLB to look into altering the definition of a strike for the first time since 1996 to raise the bottom of the zone — a shift that would be made easier by the very technology and teaching tools that have effectively lowered where pitchers now can glean strikes.

But for the time being, there is only a new, more challenging reality for hitters.

“Pitchers are better and the strike zone is bigger,” said Red Sox first baseman Mike Napoli. “And we wonder why runs scored are down?”