Major League Baseball is considering altering the textbook definition of the strike zone for the first time in nearly two decades, fearful that the proliferation of the low strike has sapped too much offense from the game, league sources told Yahoo Sports.

View photos The Royals' Nori Aoki swings through a low pitch. (AP) More

Concern around baseball about the strike zone filtered down to the MLB’s Playing Rules Committee, which must formally adopt a rules change before it’s implemented. The committee will pay close attention to the size of the strike zone in 2015 with an eye on change as early as 2016 after studies showed it has expanded significantly since 2009, coinciding with a precipitous dip in run scoring. Of particular concern, sources said, is the low strike, a scourge not only because it has stretched beyond the zone’s boundaries but is considered a significantly more difficult pitch to hit.

Runs per game fell to 4.07 in 2014, the lowest mark since 1981 and the 13th fewest since World War II, and studies from The Hardball Times' Jon Roegele and Florida professor Brian Mills pegged the low strike as a significant culprit.

Since 2009, the average size of the called strike zone has jumped from 435 square inches to 475 square inches, according to Roegele’s research. The results: Pitchers are throwing more in the lower part of the zone, and hitters are swinging at an increased rate, knowing the tough-to-drive pitches will be called strikes.

Roegele’s study estimated 31 percent of the offensive drought could be attributed to the strike zone while Mills estimated it’s between 24 percent and 41 percent. After seeing a strong correlation among the size of the strike zone, all-time-high strikeout rates and historically low walk rates, members of the committee now are fairly certain the relationship is causative, too, and seem primed to do something about it.

[Yahoo Sports Fantasy Baseball: Sign up and join a league today!]

The problem, sources said, stems from technological leaps that caused unintended consequences. In 1996, when the league last changed the strike zone to extend it from the top of the knees to the bottom, beneath the hollow of the kneecap, it did so to encourage umpires to call knee-level strikes. The lower end of the zone, in practice, was about three-quarters of the way down the thigh, so the idea was that by adjusting the eye levels of umpires to look lower, the result would be a more traditional strike zone.

Then along came Questec, the computerized pitch-tracking system, followed by Zone Evaluation, the current version tied in to MLB’s PITCHf/x system. With a tremendous degree of accuracy – especially in recent years – the systems tracked textbook balls and strikes, and the home-plate umpires’ performances were graded on a nightly basis. Over time, not only did umpires’ strike zones move down to the knees, they went to the hollow and even a smidge below.

“I don’t think the Playing Rules Committee at the time of the last change ever expected that the umpires would call strikes at the hollow of the knee,” said Mets general manager Sandy Alderson, the current chairman of the committee. “To their credit, the umpires now are.”

View photos The strike zone has lowered about three inches since 2009. (Hardball Times) More

Story continues