In 1941, Ted Williams batted a remarkable .406. Seventy-five years later, that performance sticks out for two reasons.
Most obviously, no Major Leaguer has reached the .400 plateau since. But Williams' prowess at the plate that season, combined with an opposing manager's desperate creativity, also helped establish a strategy that today is increasingly popular and hotly debated.
Over the first four months of the 2016 season, big league teams aemployed a defensive shift in more than 20,000 plate appearances, according to Baseball Info Solutions data available at FanGraphs.com. That puts the league on a pace to shatter last year's record of 24,486 shifts, continuing a steep upward trend.

This dynamic can be traced back, in part, to Williams. On July 23, 1941, the Red Sox hosted the White Sox at Fenway Park. Williams, who had yet to turn 23 years old, had batted .327 as a rookie and .344 in '40, and he entered this day at .397, with a 1.208 OPS.
Play MLB.com's ".406 contest"
Looking for a different way to defend the eventual American League MVP Award runner-up, Chicago manager Jimmy Dykes reportedly set his defense in a way that wouldn't look out of place against present-day Boston slugger David Ortiz. The third baseman moved toward the shortstop's usual spot, the shortstop shifted to the right side of second base, and the second baseman played out in short right, with the outfielders also sliding in that direction.
The results were mixed. In his account of the game, the Boston Globe's Gerry Moore wrote that in one at-bat, "With the White Sox playing Ted in a lopsided manner towards right, the Kid lined a two-bagger into the extreme left-field corner." But later, according to Moore, Chicago second baseman Bill Knickerbocker threw out Williams at first after fielding a grounder in short right field.
Williams finished 2-for-5, and he did the same the next day against the White Sox. According to Mike Vaccaro of the New York Post, Williams also beat the shift with a bunt down the third-base line, and Dykes soon gave up the strategy.
This wasn't actually the first recorded instance of the shift. In the 1920s, some managers moved their defenses around to the right side against another dead pull left-handed batter, the Phillies' Cy Williams, according to a Society For American Baseball Research (SABR) profile. This Williams, who batted .320 from 1920-26, reportedly admitted, "I couldn't hit a ball to left if my life depended on it."
But Ted Williams became the most well-known target. In fact, the "Ted Williams shift" -- an extreme version with six defenders stationed on the right half of the field -- was born when Indians player-manager Lou Boudreau tried it in July 1946.
Despite missing the previous three seasons to serve in World War II, Williams hit .342 and took the AL MVP Award that season. However, he went a modest 5-for-25 in that year's World Series, which the Cardinals won in seven games, with St. Louis skipper Eddie Dyer employing his own versions of the shift.

After Williams' career, teams continued the practice against certain hitters. In a 1978 article in The Washington Post, for example, Thomas Boswell wrote about lefty sluggers such as Willie McCovey and Boog Powell facing versions of the shift. (McCovey once countered with a bunt down the left-field line that earned him a double and scored Willie Mays from first base.)
Over the past five years or so, the technology to track shifts has come about as shift deployment has skyrocketed. That drastic increase in popularity would suggest that the strategy has been a rousing success, and indeed, a recent FiveThirtyEight.com study found some evidence of the shift hurting offensive production.
Still, when it comes to batting average, it's difficult to argue that hitters as a group are suffering from shift-related problems. This season, for example, Major Leaguers have combined for a .300 average on balls in play (BABIP). That figure actually rises to .305 against shifts.
Many top left-handed hitters who see a significant number of shifts also seem to have no trouble handling them. National League batting leader Daniel Murphy (.355), for example, owns a .349 BABIP, including .361 in 95 at-bats against the shift. Ortiz (.332) leads all hitters with 248 shifted at-bats, and his .331 BABIP in those chances is higher than his overall mark. Others, such as Robinson Canó and Carlos González, have been similarly successful.
"I guess now it's part of the game," Ortiz told the Globe last year. "I don't really put attention to it anymore. I just let the ball get deep, put a good swing on it, and whatever happens, happens."

On the other hand, the shift has hurt certain hitters over the years. Take Mark Teixeira. Opponents have shifted against the switch-hitter more than 1,000 times since 2010 -- putting him seventh in MLB -- and he has posted a .229 BABIP in those situations, compared with .261 against no shift. Current Yankees teammate Brian McCann has faced a shift a similar number of times and experienced an even bigger BABIP gap -- .237 when shifted vs. .281 when played traditionally.
What those numbers also don't account for is balls not put in play, and it's certainly possible that a shifted defense could cause a batter to change his approach enough to force more strikeouts. That could depress batting average without hurting BABIP.
But regardless of any of those stats, and the strategy's many critics, it seems clear that the shift isn't going away any time soon. Three-quarters of a century after the White Sox tried and failed to interrupt Williams' quest for .400, it's a bigger part of the game than ever.