The number of four-strikeout frames -- made possible when a hitter takes first base after a third strike is dropped by the catcher plus either first is vacant or there are two outs -- has grown exponentially in the 21st century. While there were no such achievements by a pitcher in nearly four decades from 1917-55, there were four in 2017, six in 2016 and five more in 2021.

In September 2012, there were three 4-K innings in two days, including a pair on Sept. 26. And in 2015, Dodgers pitchers accomplished the feat on consecutive days.

"This time I didn't even notice," Zack Greinke said in 2014 after his second career four-strikeout inning. "I still wasn't pitching as well as I wanted ... and I was wrapped up in ... making sure it's not a big inning."

Below is a list of every pitcher who

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