Baseball Prospectus Unconventional Wisdom

The Red Sox' Daisuke Matsuzaka (right) is off to what appears to be a great start (8--0, 2.40 ERA). Look deeper and you find that his underlying performance hasn't been nearly as gaudy. Matsuzaka is tied for the AL lead in walks (38), and his approach is maddening. He has Felix Hernandez's stuff but nibbles like Livan Hernandez. His ERA has remained low for two reasons. First, his rate of home runs allowed per fly ball is ninth-lowest in the AL (6.5%), leading to just four long balls this year. That figure is usually around 10% for the league. Second, his batting average allowed on balls in play is .236, well below the league average. The home run rate is likely to go up, and unless Matsuzaka improves his walk rate, his ERA will rise quickly as he allows more hits and homers.

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