From BR Bullpen
Pat Doyle (Patric Doyle) is a minor leagues researcher and the author of the Professional Baseball Players Database. Version 6.0 (distributed in 2005) includes minor league statistics for every season from 1922-2005. The statistics included are very limited (batting average, HR, RBI, W-L record, ERA) and the database contained errors, but it represented the best available tool to track a player's career or find basic statistics on career minor leaguers. The database was expanded several times over the years and continues to be a leading resource for minor league research.
In 2007, Doyle released a statistically expanded version of the database, called the "Professional Baseball Players Statistical Database, Version 1, which covered from 1920 to 1929, with greatly expanded statistical coverage (all available statistics, including positions played), has corrected all reported errors, continues the refinement one of the best tools to track minor league careers. A second version of the expanded database was released in February 2008, covering 1920 through 1945.