This is a good illustration of why you should use K% instead of K/9. By K/9 in 2017, his rate only dropped by 0.2 in the second half, or 2 strikeouts over those 74.1 innings. But because he gave up more hits and walks (meaning, more batters faced without recording outs/innings, thus not increasing the denominator of K/9), his K% dropped by 2.2, or 7 strikeouts over those 74.1 innings. Likewise, K/9 overstates his strikeout gains in the 2nd half of 2018. By K/9 he had 10 extra strikeouts, but by K% he had only 3.5. In 2019 so far, it's closer because his WHIPs are closer. By K/9 he's gained 7.7 extra strikeouts, while by K% it's 6.7.