The 113th World Series has already featured starts by Clayton Kershaw and Justin Verlander -- as marquee a pair of aces as it gets in today's game -- trying to crown their legacies with the championships they've long desired.
But in 2017, the Year of the Breaking Ball, the Fall Classic may ultimately come down to which side masters the curveball and slider -- both from the mound and at the plate.
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Kershaw utilized his mix of sliders and curves to near perfection in Game 1. He threw a breaking pitch more than 50 percent of the time in giving the Dodgers the series lead. Rich Hill, whose own mastery of the curveball helped him resurrect his career a year ago, allowed one run over four innings in Game 2, throwing 38 percent curveballs, though the Astros evened the series.
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Now the Dodgers will have to do what the Yankees couldn't in Game 7 of the American League Championship Series: Overcome the cavalcade of curveballs they'll see from Astros starters Lance McCullers in Game 3 and Charlie Morton in Game 4.
The Astros and Dodgers were two teams built in part on the breaking ball, staying "ahead of the curve" on what's been a growing trend across the game: Seven of the top eight teams in terms of curveball usage (Indians, Dodgers, Red Sox, Astros, Cubs, Twins, and D-backs) earned postseason spots.
Perhaps because we've seen hitters adjust to the increased velocity across the game, pitchers are turning to breaking balls. Major League usage of curveballs, knuckle curves and sliders in the regular season has jumped 3.1 percent over the past three years. That might not sound like a big change, but with more than 700,000 pitches thrown per MLB season, a three percent increase is equivalent to about 25,000 more breaking balls. The spike is even more pronounced when the calendar flips to October.

Going back to Game 7 of the ALCS, the Astros' tandem of Morton and McCullers combined to throw breaking balls (specifically curves in their case) for an astonishing 60.2 percent of their pitches -- including, famously, the last 24 pitches of the game by McCullers. That was the highest rate for any team in any game -- regular season or postseason -- on record since 2008.
But that only tells part of the story. Six of the top 10 postseason games since 2008 in terms of a single team's breaking ball usage have come in the past two seasons, including three appearances by the '16 Indians and three more combined from the Astros and Yankees this October. When looking at all games played in the past decade -- from Opening Day '08 season to the final out of the '17 ALCS -- seven of the top 10 breaking-ball contests have come in the last two years.
Now, with the Astros having evened the series with a Game 2 win, their season depends once again on what McCullers and Morton do with their curveballs in Games 3 and 4. The middle games of this World Series will be decided on breaking balls, which is only fitting seeing how those pitches have in part determined who's gotten this far. The top three starting rotations in terms of regular season breaking ball usage were the final three teams left standing this October -- the Yankees, Astros and Dodgers. Houston's bullpen, featuring pitchers like Ken Giles, Will Harris and Luke Gregersonthrew more curves and sliders than any other team's back-end unit.
Look no further than the starting matchups in this World Series to find leaders of this "breaking ball revolution." Kershaw threw breaking balls on more than half of his pitches this year, topping all qualified starters, and continued with that approach while striking out 11 Astros in Game 1. McCullers went to the curveball more than anyone, followed by Hill.

"I'm amazed by it, because it's such a strike pitch for both of them," Astros manager A.J. Hinch said of both Hill and McCullers. "You can't assume fastball in [a] 3-0 [count]. You can't assume fastballs ever against those guys. The comfort level they've both been able to establish is remarkable."
Four of the Majors' top 10 starters in overall breaking ball usage (Kershaw, Hill, Brad Peacock and McCullers) figure to appear in this Fall Classic, as will three of the top 10 in curveball usage (McCullers, Hill and Morton). These pitchers don't just lean on breaking balls, they do it with incredible skill; four of the top five curveball throwers in terms of average spin rate are featured in this series. That includes Verlander, who's known more for his fastball/slider combination than his curve.
"I don't view my curveball as complementary stuff," McCullers told Sports Illustrated back in May. "Now it's about pitchers challenging guys with their best pitch, and that means a lot of curveballs."
On the other hand, the World Series could turn on a majestic walk-off home run, too. The top two teams in slugging percentage against breaking balls this year? You guessed it -- the Astros and the Dodgers.