The Lefty-Righty theory . . .

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Did you ever wonder what the REAL effect of the lefty-righty theory is? It varies with each matchup, of course, but the ability of XERA to translate standard data into run production (Earned Run Average), shows the real overall effect of platooning. Here's the actual data from the 2007 season:

Overall MLB ERA: 4.47 RHB vs RHP: 3.97
RHB: 4.39 xxxxxxxxxxRHB vs RHP: 3.97
LHB: 4.60 xxxxxxxxxxRHB vs LHP: 4.84
RHP: 4.41 xxxxxxxxxxLHB vs RHP: 4.66
LHP: 4.62 ....................LHB vs LHP: 3.63

RHB = Right-handed batters. LHB = Left-handed batters. RHP = Right-handed pitchers. LHP = Left-handed pitchers. Other seasons have drawn (relatively) similar conclusions.

You can get a much more detailed breakdown of XERA and all the lefty-righty data at http://www.xera-baseball.com/.

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