Here's why Boston is poised to hit Buehler

There's no questioning Walker Buehler's stuff. The electricity flows into the strikeout numbers -- he has at least seven in each of his three postseason starts, including seven in 4 2/3 innings of one-run baseball in the Game 7 win that clinched the National League pennant for the Dodgers.
But in Game 3 of the World Series at Dodger Stadium on Friday, he'll face a Red Sox offense that's unlike the Braves, or the Brewers, or really any team in Major League Baseball. Boston's lineup is going to pose a unique challenge for the 24-year-old flamethrower, for one big reason: The Red Sox crush high velocity.
As a starting pitcher, Buehler had an average fastball velocity of 96.1 mph during the regular season. Of the 170 starters who threw at least 500 fastballs, he was one of only seven who averaged at least 96 mph. (In the postseason, Buehler's average velocity is up to 97.2 mph, tied with Gerrit Cole for third highest among playoff starters behind Nathan Eovaldi and Luis Severino.)
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But the Red Sox were MLB's best hitting team this year against fastballs in Buehler's high-velocity territory.
Statcast™ has a metric called expected wOBA to reflect overall offensive performance and the quality of contact a hitter is making. It considers the exit velocity and launch angle of all a hitter's batted balls, plus walks and strikeouts. In 2018, against fastballs 96 mph or faster -- that is, at or above the velocity of an average Buehler fastball -- the Red Sox had the best xwOBA of any team by a wide margin.
Highest team xwOBA vs. 96-plus-mph fastballs in the 2018 regular season
1. Red Sox: .360

2. Nationals: .336
   
3. Dodgers: .335
   
4. Cardinals: .324
   
5. Blue Jays: .323
   
6. Braves: .292 (Buehler's NLDS opponent)
   
7. Brewers: .287 (Buehler's NLCS opponent)
   League xwOBA vs. 96-plus mph fastballs: .302
   The Red Sox were 24 points of xwOBA better than the next-closest team. (For reference, xwOBA is scaled the same as on-base percentage.) They were nearly 60 points better than league average. They were almost 70 points better than the Braves team Buehler faced in the NL Division Series and more than 70 points better than the Brewers team he faced in the NL Championship Series.
   Mookie Betts and J.D. Martinez led the way. Martinez was one of the best hitters at handling high velocity this season, with a .484 xwOBA against fastballs thrown 96 mph or harder. Betts was at .372.

The Red Sox also rarely swung and missed, even against fastballs at that high velocity. They whiffed on only 18.7 percent of their swings against 96-plus mph fastballs, the second-lowest rate of any team. That could make a big difference against a strikeout-oriented pitcher such as Buehler, who got 88 of his 151 strikeouts on fastballs during the regular season -- and has gotten 16 of his 22 postseason strikeouts -- nearly 75 percent -- on fastballs. 
Lowest team whiff rate* vs. 96-plus mph fastballs in the 2018 regular season

1. Indians: 17.6 percent
   2. Red Sox: 18.7 percent
   
2. Marlins: 19.5 percent
   
3. Cardinals: 19.8 percent
   
4. Nationals: 20.2 percent
   League average whiff rate vs. 96-plus mph fastballs: 23.5 percent
   *Whiff rate: Percentage of swings missed

The Red Sox have continued to make excellent contact against high-velocity fastballs in the postseason. Entering the World Series, their xwOBA against 96-plus mph heat was .403, the highest of any team in the playoff field. They whiffed on only 20.3 percent of their swings, the second-lowest rate of the teams to reach at least a Division Series (behind the Astros).
There's one more key factor to address: Buehler's fastballs aren't just high-velocity. His four-seamer, specifically, is also high-spin. Buehler's average four-seam fastball spin rate as a starting pitcher in the regular season was 2,414 rpm, 11th highest among 113 starters who threw at least 500 four-seamers -- and much higher than the MLB average of 2,263 rpm. It's been right about the same in the playoffs, averaging 2,400 rpm -- sixth highest among playoff starters. High-spin four-seamers tend to be harder to square up, inducing more swings-and-misses and popups.

The problem is, the Red Sox still hit them. Facing fastballs that were both high-velocity and high-spin -- 96-plus mph and 2,400-plus rpm -- they had a .353 xwOBA in the regular season, which was again the highest of any team. In their smaller playoff sample, they're at .388.
As far as whiff rate goes, Boston did have more swing-and-misses when adding in the high-spin component, but its 24.5 percent whiff rate against high-velocity/high-spin four-seamers in the regular season was still seventh-lowest in MLB. The Red Sox are at 24.3 percent in the playoffs.
All this boils down to a major matchup concern for Buehler. So how can he attack the Red Sox's hitters? This might be his best chance: his curveball.
The Red Sox's offense doesn't have many holes. They're one of the best hitting teams against each category of pitches -- fastballs, breaking and offspeed. They hit for average and power, they make contact at a high rate and they don't chase bad pitches.
But one area Boston showed just a sliver of vulnerability is against high-spin curveballs, and Buehler has one. The MLB average curveball spin rate in 2018 was 2,492 rpm. Buehler's averaged 2,756 rpm as a starter in the regular season, and it is averaging 2,800 rpm in the playoffs. More spin on a curveball generally means more movement and better outcomes for the pitcher.

From an xwOBA standpoint, the Red Sox were still strong against high-spin curves this season -- their .258 mark against curveballs with spin rates of 2,700 rpm or higher ranked sixth in MLB. But they didn't make quite as much contact, and they weren't quite as disciplined as usual.
Against 2,700-plus rpm curveballs, the Red Sox whiffed on 34.9 percent of their swings this season, ranking 17th in MLB. When they were thrown 2,700-plus-rpm curveballs out of the strike zone, they chased 30.7 percent of the time, 21st in MLB.
The Red Sox did just beat an Astros pitching staff built on high-velocity, high-spin, fastball-curveball pitchers like Buehler: Justin Verlander, Cole and Charlie Morton in the rotation, Ryan Pressly and Lance McCullers Jr. in the bullpen. But their results against Houston's curveballs were a mixed bag.
Martinez, for instance, struck out in his first four plate appearances decided on curveballs in the series, but then adjusted and singled twice and homered in his next three. On the other hand, Betts went 0-for-2, Jackie Bradley Jr. and Steve Pearce went 0-for-3, and Andrew Benintendi went 0-for-7. All those curves had spin rates over 2,700 rpm. For Buehler in the World Series, that can at least be a starting point.