I’m actually embarrassed to ask this simple baseball question, but I honestly don’t know the answer.
If a pitcher goes seven complete innings and then gets the first two outs of the next inning and then leaves the game, he’s credited with 7.2 innings, no?
OK, in his next start he gets the first two outs and then leaves the game.
Is his total now 8.1 innings pitched (or could it possibly be 7.4)?
Of course not. The .2 does not represent 2/10 of an inning. It’s just notation for 2/3 of an inning. If the pitcher gets two more outs, then he would’ve pitched 8 and 1/3 innings, so it’s 8.1 innings in baseball shorthand notation.
The listings of innings pitched all depends upon what you need the number for. Usually for box scores, the listing will be 6.1 or 6 1/3. Bigger databases will use 6.3 because they assume you might be doing some number crunching.
Those thirds of an inning, of course, are outs. If a pitcher is doing fine until the 5th inning, and he gives away two hits and walks three batters without making an out before he is replaced, he not credited with any part of the 5th inning.
The notation originated in newspapers, because printing thirds of a inning required a typesetter to layout “8-1/3”, which took more space than “8.1”. Saving space was also the motivation that led many newspapers to give sports teams their own nicknames – calling the Athletics the A’s or the Pirates the Bucs.