MLB Receives Report on Increased Home Run Rate

From an MLB press release:

Major League Baseball has received the results of a study conducted by a committee of scientists on the causes of the increased home run rate in the game since 2015.  The committee, assembled by Commissioner Robert D. Manfred, Jr. in August 2017, was comprised of the following experts:

  • Alan Nathan (Chairman) – Professor of Physics Emeritus, University of Illinois
  • Jim Albert – Professor of Statistics, Bowling Green State University
  • Jay Bartroff – Professor of Mathematics, University of Southern California
  • Roger Blandford – Professor of Physics, Stanford University
  • Dan Brooks – Owner of
  • Josh Derenski –Ph.D Student, Marshall School of Business, University of Southern California
  • Larry Goldstein – Professor of Mathematics, University of Southern California
  • Peko Hosoi – Professor of Mechanical Engineering, Massachusetts Institute of Technology
  • Gary Lorden – Professor Emeritus of Mathematics, California Institute of Technology
  • Lloyd Smith – Professor of Mechanical & Materials Engineering, Washington State University

The committee investigated a number of hypotheses, including the properties of the baseball, weather conditions and changes in player behavior.  The research included a detailed analysis of Statcast data, as well as an investigation of the properties of the baseball that can affect home run production, including an inspection of Rawlings’ production plant in Costa Rica.  The committee set its own agenda and arrived at their own conclusions and recommendations, independent of the Commissioner’s Office.

The committee concluded that the increase in home run hitting since the 2015 season was due, at least in part, to a change in the aerodynamic properties of the baseball (i.e., reduced drag for given launch conditions, as opposed to a change in launch conditions).  That conclusion is supported by their analysis of Statcast data, a physics-based model that the Committee developed, and laboratory testing of game-used baseballs from before and after the increase in home run rate.  The Committee did not find any change in the size, weight, seam height, or COR of the baseball that would explain the increase in home runs.  Though the Committee was unable to conclusively prove the exact cause of the reduced drag since the 2015 season, they offered hypotheses including that the rubber pill may be more centered within the baseball since 2015 and that the ball may be staying rounder while spinning since the 2015 season.

Importantly, the committee also concluded that no change to the materials or manufacturing process, whether intentional or unintentional, has played a significant role in the home run surge.

Based on the results of the study, the Commissioner is taking the following actions:


  1. Monitoring of Temperature and Humidity Conditions. The Commissioner’s Office is monitoring temperature and humidity in the ball storage locations of the 30 ballparks and will work with the committee on whether to require the use of humidors at all ballparks for the 2019 season.
  2. Review of Production Specifications of Baseballs.  The Commissioner’s Office is working with Rawlings to make updates to the existing production specifications of baseballs and to develop additional specifications for the aerodynamic properties of the ball.
  3. Perform Aerodynamic Testing on Baseballs.  In addition to the existing testing protocol, the Commissioner’s Office is working with the committee to develop a set of aerodynamic tests for game baseballs.
  4. Create Standards for Mud Rubbing.  The Commissioner’s Office is providing Clubs with guidance on the appropriate mud rubbing of baseballs, which will be enforced by the umpires.
  5. Formation of a Scientific Advisory Council.  Some members of the committee will continue to advise the Commissioner’s Office on issues related to baseball performance, as well as other science-related topics.

Commissioner Manfred said: “I thank the committee for all of its hard work on this important issue.  Based on the results of their study, I am accepting their recommendations immediately and look forward to their continued guidance in this area.”

The full report is here.

Clayton Kershaw leaves start after two innings with back injury.

Clayton Kershaw

Clayton Kershaw didn’t allow a hit Sunday before he was forced to leave with low back tightness. (Getty Images)

LOS ANGELES — It was 86 degrees Sunday in Los Angeles when Clayton Kershaw sat down uncomfortably in the dugout after pitching the second inning. A Dodgers trainer approached him. After a quick chat the two walked down the tunnel leading into the home clubhouse. Quietly, Kershaw’s day was done.

The Dodgers announced that Kershaw left the game with right lower back tightness.
Continue reading “Clayton Kershaw leaves start after two innings with back injury.” »

A brief Pedro Guerrero update.

Two days after he was transferred out of the intensive care unit of his Manhattan hospital, former Dodgers slugger Pedro Guerrero was able to talk, and move his arms and legs Thursday, according to a friend of Guerrero’s family.

Guerrero, 60, suffered a brain hemorrhage while driving to the gym on Monday in Queens. He was taken to the nearest medical facility that night and placed in a medically induced coma, then transferred to Lenox Hill Hospital the next day. Guerrero awoke from the coma Tuesday and has been steadily progressing since. A second source in contact with Guerrero’s family said that the slugger is now aware enough to recite his date of birth.

Dodgers add three to 40-man roster.

The Dodgers added three players to their 40-man roster on Friday: pitchers Chase De Jong and Jacob Rhame and catcher Kyle Farmer.

The deadline for teams to add certain minor league players to the 40-man roster in order to prevent them from being eligible for the Rule 5 draft was 5 p.m. Had they not been added today, the Dodgers would have risked losing De Jong, Rhame and Farmer.

De Jong went 14-5 with a 2.86 ERA for Double-A Tulsa, earning Texas League pitcher of the year honors. The right-hander also made three starts for Triple-A Oklahoma City.

Rhame had a 3.24 ERA in 59 appearances out of the bullpen at Triple-A Oklahoma City this year. The 23-year-old right-hander saved seven games and could reprise the closer’s role in 2017.

Farmer, 26, slashed .255/.323/.395 in 74 games at Double-A Tulsa this season.

Dave Roberts is the 2016 National League Manager of the Year.

Dave Roberts

Dodgers manager Dave Roberts won the NL Manager of the Year award on Tuesday. (John McCoy/Staff photographer)

Dave Roberts, who guided the Dodgers to 91 wins and a division title in his first season managing at any level, was named National League Manager of the Year on Tuesday. Roberts was listed first on 16 out of 30 ballots. The Baseball Writers’ Association of America voted on the award after the regular season.

Roberts’ own struggles on his journey to the big leagues helped him relate to his players, writes colleague Bill Plunkett.

Chicago Cubs manager Joe Maddon finished second to Roberts and was listed first on my ballot. Here’s why.