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That wonderful resource of all things random and interesting, has the splits for days of rest - and even breaks it down between starting and relieving. For Laffey's career, he has a .748 OPS against on 2 days or less rest, and a .513 OPS against on 3+ days. Of course you have to remember that Laffey's career hasn't been long yet, and he's started for the lion's share of his major league innings, so those samples are around 150 and 90 PA respectively.