In early games that started before 7 p.m., the earned run average (ERA) of pitchers who were morning types (3.06) was lower than the average ERA of pitchers who were evening types (3.49); however, in games that started at 7 p.m. or later, pitchers who were evening types performed slightly better (4.07 ERA) than morning types (4.15 ERA). The study involved 18 pitchers from five MLB teams, using the players' statistics from the 2009 season.