20 July 2011

MLB Projections

I've tweeted a little bit about this earlier this week, so here's the fruits of my labor. I've developed a little bit of Excel programming skills over the past couple years, and wanted to find a way to see how bad the Cubs can b....I mean see where the MLB season might end up at the end of the regular season. The two main components I would need are a measure of teams true ability to win games, and a predictive formula for teams given their remaining schedule.

Enter the Pythangorian Win Expectation and Log5 formulas.

For those who are currently thinking of jokes of my dorkdom, Pythagorian Win Expectation (PWE) takes a team's runs scored and runs against, and spits out an expected win percentage. It gets its name from looking somewhat like that old Pythagorian Theorem we all learned in trigonometry (a^2 + b^2 = c^2):

PWE = (R^2) / (R^2 + RA^2),

where R is runs for and RA is runs against. Further research on the subject showed that a more accurate exponent is 1.81 instead of 2. A different exponent can also be used for college basketball (somewhere between 8 and 9) and the NBA (somewhere between 14.5 and 16).

The Log5 formula comes from the Godfather of Sabermetrics, Bill James. Based on the Bayes Theorem, this formula is used to find win probability of two teams when they meet. If Team A and Team B played each other, the probability of Team A is given by

P(A) = (A - A * B) / (A + B - 2*A*B),

where A is Team A's win percentage, and B is Team B's win percentage.

So now we have an decent estimation of a team's ability to win games, and a way to estimate the probability of who will win a game between two teams. All there is left to do is throw the remainder of the MLB schedule into the hopper and see what we come up with (h/t to Daily Baseball Data for putting the entire MLB schedule in Excel format).

American League

EAST

W

L

Boston

98.5

62.5

NY Yankees

96.1

62.9

Tampa Bay

84.8

76.2

Toronto

81.4

81.6

Balimore

63.4

96.6

CENTRAL

Detroit

84.5

77.5

Cleveland

84.3

77.7

Chicago Sox

79.3

82.7

Minnesota

72.6

88.4

Kansas City

67.1

94.9

WEST

Texas

93.5

69.5

LA Angels

82.0

81.0

Oakland

72.0

91.0

Seattle

70.5

90.5

National League

EAST

Philadelphia

100.6

62.4

Atlanta

94.1

68.9

NY Mets

81.3

81.7

Washington

79.3

83.7

Florida

75.7

87.3

CENTRAL

Pittsburgh

85.2

75.8

St. Louis

85.7

77.3

Milwaukee

84.2

77.8

Cincinnati

83.4

79.6

Chicago Cubs

64.4

98.6

Houston

57.3

105.7

WEST

San Francisco

91.1

71.9

Arizona

85.7

77.3

Colorado

79.7

83.3

San Diego

71.7

91.3

LA Dodgers

70.7

91.3


I do give my apologies, because this table was made in the middle of a day of games. I don't have time to wait until midnight for all the games to be over, nor the time in the morning to get it done before the early afternoon games start. This also skews the run totals a bit, but not a whole lot for our analysis.

In a showing of how the futile the Cubs are this year, the first thing I noticed was that they are, on average, not headed for a 100-loss season. Around the league, here now are the storylines I will be looking for the rest of the season:
  • The reigning pennant winners, the Rangers and the Giants, will run away with their respective divisions.
  • The AL East will once again take two playoff spots, leaving Detroit and Cleveland fighting for one spot while Boston, New York and Tampa fight for two spots
  • With the East Coast Bias of the media, the watch will be on to see if the Phillies will win 100 games for the first time since 1977
  • The exciting 4-team race for the NL Central, which includes the Pirates quest for their first winning season since Barry Bonds was skinny (1992).

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