A strikeout is a statistic credited to a pitcher and charged to a batter when the umpire calls three strikes on a batter, as set forth in this Rule 9.15.
(a) The Official Scorer shall score a strikeout whenever a batter:
(1) is put out by a third strike caught by the catcher;
(2) is put out by a third strike not caught when there is a runner on first before two are out;
(3) becomes a runner because a third strike is not caught; or
(4) bunts foul on third strike, unless such bunt on third strike results in a foul fly caught by any fielder, in which case the Official Scorer shall not score a strikeout and shall credit the fielder who catches such foul fly with a putout.
(b) When a batter leaves the game with two strikes against him, and the substitute batter completes a strikeout, the Official Scorer shall charge the strikeout and the time at bat to the first batter. If the substitute batter completes the turn at bat in any other manner, including a base on balls, the Official Scorer shall score the action as having been that of the substitute batter.