That was a great article.
I remember Valenzuela and McGraw and G. Hernandez, of course. But the first (and maybe because of that, I always though the best) big time screwball pitcher I saw was Mike Cuellar, when he pitched with Houston in the late 1960s. Cuellar was an average-sized guy with average looking pitches otherwise; luckily, he threw his screwball - which was exceptional - a lot.
Cuellar had some good years in Houston, on not-so-good teams: but I guess Spec Richardson, et al, thought he was getting old (he was 30-something.) So after the 1968 season they traded him to Baltimore, for Curt Blefary. Blefary was a versatile hitter with some power, and younger than Cuellar by 6-7 years; and he had a pretty decent year for his one full season as an Astro. Meanwhile, Cuellar averaged 20 wins a year for the next seven years as an Oriole, until he was damn near 40.
Talk about your bad Spec Richardson trades.