A Golden Sombrero is a term given to a batter that strikes out four times in a game. Not a good thing to have happen. But, if you are a pitcher and you strike out 4 batters in an innings, this is a good (and rare) thing.
The latest to do it was Kenley Jansen for the Dodgers.
How does one accomplish this? The trick is to have one of the victims reach base.
6.05 A batter is out when—
b) A third strike is legally caught by the catcher;
(c) A third strike is not caught by the catcher when first base is occupied before two are out;
Unless first base is occupied with less than 2 outs, the catcher has to cleanly catch a pitch for the batter to be out. If he does not, then the batter becomes a runner and can attempt to reach first base.
This rule is a holdover from the days when the catcher would play deep behind the plate. Any out on a batter had to end with “ball in hand”. With the catcher back so far, this came into play. It is a rarity in modern baseball.
Why add the provision where the batter is automatically out with first base occupied and less than 2 outs? If this was not the case, the catcher would intentionally drop the ball and start a double play.
In this inning, the first batter strikes out and reaches base. The pitcher then strikes out three more.
How rare is it to pitch only one inning yet get 4 Ks? Using Baseball Reference’s play index, I see this has only happened 18 times since 1914. Of course there are more instances of 4 Ks in an inning but those pitchers pitched more innings.
Page 46 of RuleGraphics covers uncaught third strikes.