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Aggression could lead to production for Sox

Betts, Bogaerts had low swing rates on in-zone pitches in 2017
January 7, 2018

Although they won the American League East championship in 2017, the Red Sox's offense lacked thump, finishing 26th in the Majors in slugging percentage (.407), 22nd in OPS (.736) and wRC+ (92) and 27th in home runs (168).Perhaps, in the second offseason of the post-David Ortiz era, Boston will acquire

Although they won the American League East championship in 2017, the Red Sox's offense lacked thump, finishing 26th in the Majors in slugging percentage (.407), 22nd in OPS (.736) and wRC+ (92) and 27th in home runs (168).
Perhaps, in the second offseason of the post-David Ortiz era, Boston will acquire some lineup reinforcements from outside the organization. Free-agent slugger J.D. Martinez is one intriguing possibility.
At the same time, the Sox could use more production from the players already on the roster. One key to that? Be more aggressive -- selectively. In other words, lineup cogs such as Mookie Betts and Xander Bogaerts could benefit from swinging more frequently at hittable pitches.
Before getting to Boston's specific case, let's establish the importance of pitch selection of hitters.
• In 2017, when batters swung at pitches beyond the edges of the strike zone, according to Statcast™'s detailed zone, they whiffed 51 percent of the time and produced a .116 weighted on-base average (wOBA). By comparison, pitchers collectively produced a .144 wOBA last season.
• When batters swung at pitches along the edges of the zone, they whiffed 25.9 percent of the time and produced a .270 wOBA -- similar to Alcides Escobar.
• When batters swung at pitches within the edges of the zone, they whiffed 14.9 percent of the time and produced a .386 wOBA -- similar to Nelson Cruz.
• And more specifically, when batters swung at pitches right in the middle of the zone, they whiffed 12.6 percent of the time and produced a .419 wOBA -- similar to Bryce Harper.
Don't swing at bad pitches, but swing at good ones. It's not rocket science, but it is difficult to execute.
The Red Sox excelled at the first half of that equation in 2017. For pitches in the first two categories -- the "pitcher's pitches" on the edges of the zone or outside it -- Boston's 35.2-percent swing rate was sixth lowest in the Majors. Among 122 individual hitters who saw at least 1,500 such pitches, Betts also finished sixth in lowest swing rate (27.8 percent).

The flip side is that when it came to taking cuts at those friendlier pitches within the edges of the zone, no club did so less often than Boston (66.6 percent, compared with the MLB average of 71.7 percent). The same goes for "middle-middle" pitches (71 percent, compared with 75.8 percent).
Of course, not every in-zone pitch is one that a batter should swing at, depending on all sorts of factors, including the count, situation and pitch type. Hitters get fooled, or get pitches they can't handle, and there is value in working counts.
Still, it's difficult to ignore how frequently talented Red Sox batters let juicy pitches go past them.
Lowest swing rate on in-zone* pitches, 2017
Min. 500 pitches (169 qualified hitters)

  1. Brett Gardner, NYY: 54.6 percent
    2. Mookie Betts, BOS: 56.7 percent
  2. Joe Mauer, MIN: 57.3 percent
    4. Xander Bogaerts, BOS: 57.9 percent
  3. Jose Iglesias, DET: 59.0 percent
    ---
    16. Dustin Pedroia, BOS: 64.0 percent
    *Excluding pitches on edges
    Among 250 batters who saw at least 100 pitches right down the middle, only Gardner and Mauer swung less often than Bogaerts (58.3 percent) and Betts (58.6 percent). Yet when those two Sox did swing, they slugged a combined .716 with 11 home runs and produced a wOBA in excess of .450.

For positive reinforcement, consider Betts' at-bat against the Twins' Ervin Santana on May 7 at Target Field. Betts got ahead in the count, 2-1, and when Santana pumped a 91.9-mph fastball right down the middle, Betts jumped on it and ripped a line drive just over the wall in left-center field. With an exit velocity of 109.8 mph, it stands as Betts' hardest homer since Statcast™ debuted in 2015.
Or how about when Bogaerts faced the Cardinals' Trevor Rosenthal with Boston facing a 4-2, ninth-inning deficit on Aug. 16 at Fenway Park. After taking a ball, Bogaerts didn't let Rosenthal even the count with a 91.4-mph fastball to the center of the zone, instead crushing a solo shot into the seats above the Green Monster.

Both Betts and Bogaerts have been more aggressive against good pitches in the past. In 2016, they each posted swing rates of nearly 63 percent against pitches inside the edges of the zone. Against offerings in the center of the zone specifically, Betts (70.7 percent) and Bogaerts (65.0 percent) also took their cuts more often that year.
These two young franchise cornerstones were both just 24 years old last season, but both saw their production with the bat slip. Betts' wRC+ dropped from 137 to a career-low 108, a bit above the league average of 100. After two straight years above a 110 wRC+, Bogaerts fell to 96.
While there certainly is no single cause for either player's slide -- or the offense's in general -- letting it fly more often instead of letting fat pitches go by would be a good step in the right direction.
In that sense, it's interesting that Boston's new hitting coach, Tim Hyers, spent the past two seasons as an assistant hitting coach with the Dodgers. L.A., one of the game's top offensive teams last year, led MLB in lowest swing rate against pitches on the edges of the zone or outside it (33.4 percent). Yet, the club also had the 11th-highest swing rate against pitches within the edges of the zone (71.9 percent).
This degree of selective aggression isn't easy to pull off, but it would come in handy as the Sox try to keep pace with the loaded Yankees in the AL East.

Andrew Simon is a research analyst for MLB.com. Follow him on Twitter @AndrewSimonMLB.