Rule 5.02 of the Official Baseball Rules declares that the catcher must be behind the plate, the pitcher must be on the mound, and every other defender must be in fair territory. And that is the entirety of what the sport’s bible says about defensive positioning. It has been this way for nearly 150 years, and until recently no one had ever considered that the rules might need to be changed.

Commissioner Rob Manfred is acutely aware of the history, but now, thanks to the accelerating evolution in the way teams are deploying their defenders – and the effect it appears to be having on the way the game is played – he is in the unenviable position of having to consider implementing a limit or outright ban on defensive shifts, a move that would constitute the game’s most monumental rule change since the American League introduced the designated hitter in 1973.

There is a growing body of evidence that the game’s timeless but tenuous equilibrium has been thrown off. While strikeouts are at an all-time high and still rising, the leaguewide batting average of .245 entering the weekend was the lowest it has been in 46 years and roughly the same as it was in 1907, in the heart of the Dead Ball Era. The rate of 8.34 hits per team-game is roughly that of the mid-1960s, years in which the decline in offense ultimately led MLB to lower the height of the mound. There are fewer balls in play than at any other point in the game’s history.

Meantime, the use of shifts – commonly defined as at least three infielders on one side of the second-base bag, and an accepted part of baseball strategy that first came to prominence when teams deployed it against Ted Williams in the 1940s – is at an all-time high, with defenses using it in more than 17 percent of all plate appearances this season.

A handful of pull-happy hitters now face a shift in more than 90 percent of their plate appearances, and the trend saw its most radical manifestation earlier this year when the Houston Astros – the most aggressive franchise in the game in the use of shifts – first deployed six defenders, including all four infielders, to the right of second base against Texas Rangers slugger Joey Gallo. In his first at-bat against the alignment, he grounded into the heart of it.

Manfred first broached the notion of banning shifts on his first day in office as Bud Selig’s successor, telling ESPN on Jan. 25, 2015, “Things like eliminating shifts – I would be open to those sorts of ideas.” Last week, in an interview with The Athletic, he went even further, saying, “There is sentiment in the game for the idea that we need to be more aggressive about the managing the trends that have been introduced in the game, at least partly based on analytics . . . [B]ecause the trends seem to be persistent, I think we’re at a point in time that we do need to think about and really analyze hard some potential changes.”

What was most interesting about these comments 3 1/2 years apart was the divergent reactions. In 2015, Manfred’s initial suggestion about limiting shifts was met with widespread outrage. But this time, some prominent figures are lining up behind the commissioner.

“If they came to me and said, ‘Would you like to outlaw the shifts?’ – I would say yes,” Kansas City Royals manager Ned Yost told reporters. “Go for it.”

St. Louis Cardinals manager Mike Matheny, a member of Manfred’s panel tasked with studying ways to improve the pace and quality of play, told reporters, “I think there may be a rule change one day, potentially. . . . I wouldn’t be opposed to [it].”

Other sports have changed their rules over the years to halt the advances in defense over offense – the NHL, for example, with its crackdown on the neutral-zone trap, or the NBA with its limitations on zone defenses – but baseball has always fancied itself as different, its game as it is played on the field remaining virtually unchanged for more than a century. Even an alteration as seemingly minuscule and unobtrusive as introducing the automatic intentional walk, as Manfred did in 2017, was met with an outcry that dwarfed the rule’s actual impact.

But this time, circumstances may be forcing a monumental change.

The two major trends in the sport – the increase in shifts and the drop in batting average and hits – are almost certainly not coincidental. And Manfred is beginning to suspect a third trend – a nearly seven percent year-to-year drop in leaguewide attendance – is also related to the lack of action on the field (as well as the organizational strategy of downsizing, or “tanking”), telling reporters Thursday he is “concerned that there’s something more to it than weather.”

When Manfred first floated the notion of a limit on shifts 3 1/2 years ago, his hope was that it would never have to come to that, and that the cardinal rule of hitting – “Hit it where they ain’t” – would dictate offensive strategy, with hitters beating the shift by going to the opposite field, or even bunting against it, until defenses began to adjust back the other way. But despite the occasional example – even Gallo bunted to the left side for a single against the Astros earlier this month – the strategy has not taken hold.

“The hope always is the game is going to self-correct,” Manfred told The Athletic last week. “. . . People said, ‘They’re going to learn to hit the other way. They’re going to bunt.’ We just haven’t seen those changes.”

But before making a radical change to the rule book, MLB should tread carefully – and examine, for one thing, whether the increase in the frequency and degree of defensive shifts is a cause of the decline in hitting, or an effect.

In other words: Did the rise of the shift force hitters to adopt an all-or-nothing approach at the plate to hit the ball over the defense? Or was it the rising popularity of that plate approach, brought about by the constant rise in velocity and strikeout mentality on the part of pitchers, that forced defenses to adopt shifts, with varying degrees of extremity, against a higher number of hitters?

Baseball should also consider whether a less obtrusive, alternative measure – perhaps a tweak to the strike zone, which has seen a fair degree of fluidity over the decades – might help remedy the problem without requiring a monumental change.

Rule 5.02, like much of baseball’s rule book, is beautiful in its simplicity and its endurance. To change it would be to acknowledge the sport is broken, and there is no other way to fix it.