Overview
A quality start (QS) is credited when a starting pitcher completes at least six innings while allowing three or fewer earned runs. Sportswriter John Lowe coined the term in 1985. Unlike wins, which depend on run support and bullpen performance, QS more accurately reflects a starter's individual consistency. In NPB, QS rate (QS divided by starts) has gained traction as a key evaluation metric alongside the spread of sabermetrics. A QS rate above 60% marks a reliable rotation member, while 70% or higher signals ace-caliber performance. Critics note that six innings with three earned runs equates to a 4.50 ERA, prompting the use of the stricter high-quality start (seven or more innings, two or fewer earned runs) as a complementary measure.