A pitching statistic in baseball that measures the number of innings on average a starting pitcher pitches on average each time they start a game. Innings per Game Started is arrived at by dividing the total number of innings pitched (career/season) by the amount of games started by the pitcher. For example, if a pitcher had 200 innings pitched over 35 games started the pitcher would have a 5.7 I/GS.
I/GS is an important statistic to approximate the amount of work you will get out of your starting pitcher on average. The I/GS numbers can identify the workhorse pitchers in a team rotation who are good at pitching through many innings without letting the other team generate significant runs. If a pitcher is getting beat up and allowing runs their manager rarely waits too long to bring in a reliever. Consequently, pitchers with high I/GS numbers represent the better pitchers in the league.