Whether you’re watching a game at the ballpark or on TV, you will often see the defense do something that might seem strange.

Rather than playing what might be considered their standard positions, some infielders will move to other spots when certain hitters are at the plate. This is called a shift. While a shift can take different forms, it typically involves playing three infielders on one side of the field, instead of the usual two – for example, moving the third baseman or shortstop to the right side. The goal is to position the defense where the batter is most likely to hit the ball, which in most cases means to their pull side (the right side for a left-handed batter, and vice versa).

The 2010s will be known as the decade when these defensive shifts exploded in baseball. But as new-age as shifting seems, it actually isn’t a “new” strategy at all.

Shifts can trace their lineage back nearly a century, in fact, to outfielder Cy Williams. One of baseball’s first true sluggers, Williams sat atop the National League’s all-time home runs list until 1929, when he was surpassed by Hall of Famer Rogers Hornsby. Williams knocked 251 dingers over his 19-year career with the Cubs and Phillies and proved to possess immense pull power to the Baker Bowl’s famous short porch (and Green Monster-like wall) in right field. NL managers eventually realized that the best way to defend Williams was to position their outfielders both extremely deep and over to the right -- though it might not have slowed Williams all that much, since he finished with a career .568 slugging percentage at the ballpark.

While Philadelphia’s Williams may have been the first modern player to see a shift, a much more famous Williams would encounter it with greater fanfare two decades later. Hall of Famer Ted Williams, perhaps the greatest hitter in the history of baseball, got off to one of the most prodigious beginnings to any Major League career, putting up batting averages of .327 as a rookie and .344 in his sophomore season. By the summer of 1941, the year Williams would go on to finish with his mythical .406 average, he was seemingly infallible at the plate.

Boston’s phenom owned a .397 average and 1.208 OPS on July 23, 1941, when the visiting White Sox and their manager, Jimmy Dykes, arrived at Fenway Park. Dykes sought to foil the left-handed Williams by placing his shortstop on the right side of second base and moving his second baseman to shallow right field, while also sliding his third baseman over to the shortstop area. According to Ben Bradlee’s biography of Williams, “The Kid,” Dykes’ move elicited a bemused reaction from the Splendid Splinter, who proceeded to go 2-for-5 with a double down the left-field line, and he ultimately went 4-for-10 over the course of the two-game series. Nothing could slow Williams down that summer.

But Williams’ success that week didn’t dissuade Indians manager Lou Boudreau from trying a more extreme shift against him later in the decade. After seeing Williams go 4-for-5 with three homers and eight RBIs in Game 1 of a Fenway doubleheader on July 14, 1946, Boudreau -- the Indians’ player-manager -- relayed a plan to his fellow infielders. When Williams stepped up for his first at-bat in Game 2, he saw seven of Cleveland’s eight fielders positioned on the right side of second base. Three players manned the dirt with Jimmy Wasdell directly on the first-base line, while two outfielders stood behind deep behind them by the warning track. Second baseman Jack Conway stood halfway between the two fronts, and was also shaded near the foul line. To the best of anyone’s memory, Boudreau’s “Williams shift” was an extreme measure that Major League Baseball hadn’t seen before.

Did it work? Not exactly. Williams finished that game 1-for-2 with a double and two walks. But he saw a similar approach later that year in the World Series from manager Eddie Dyer’s Cardinals, and Boudreau would inspire several more opposing managers to do the same over the remainder of Williams’ career. Williams stubbornly stuck to his hitting approach for many years, and while his career average did dip roughly 16 points once the shifting began, his .340 mark from 1946 through the end of his big league tenure suggests that mindset still worked just fine.

Shifting began popping up against other hitters in the decades that followed. Orioles slugger Boog Powell faced them, as did Hall of Fame slugger Willie McCovey -- one of the most dangerous left-handed pull hitters of all time. But the tactic didn’t really become in vogue until the new millennium, when sabermetrically-inclined thinkers began making their way into Major League front offices. Manager Joe Maddon’s Tampa Bay Rays embraced shifts at the end of the aughts, and opponents couldn’t help but take notice once their hard contact began finding the Rays’ perfectly positioned gloves.

“First, second, third game of the season, just leave Spring Training, you hit a couple of rockets and next thing you know, they’re right at somebody,” frustrated Yankees slugger Nick Swisher told The New York Times in 2012.

The Brewers had benefited from an increase in shifts to reach the NLCS the year before, but back then that “increase” still resulted in just 209 shifts across the entire season. That total seems incredibly quaint today, because the practice has positively shot through the roof over the past half-decade. In 2018, MLB teams combined to deploy a defensive shift in more than 40,000 plate appearances, according to Baseball Info Solutions, and that total jumped by more than 25,000 plate appearances in just a five-year span. Shifts today come in all sorts of formations, with four-man outfields emerging as the latest alignment in '19.

Shifts have drawn their fair share of ire from hitters and fans alike as they’ve proliferated, though the jury is still out as to how effective they truly are at stymieing sluggers. For instance, recent research from Statcast player tracking data suggests that while shifts may lower batting average on balls in play, they might also increase walks and encourage pull hitters to simply swing for the fences even more.

Indeed, when all is said and done, we may look back at this golden age of shifts and call it somewhat of a wash in the grander battle between pitchers and hitters -- just as one could with Williams in the 1940s and ‘50s. But, with baseball eternally being a game of inches, that doesn’t mean managers won’t continue to move their fielders around with hopes of gaining every possible advantage they can.