The Internet rules. Turns out last week Bill Parker did the research I wanted earlier, contextualizing that Jamie Moyer stat, and it’s awesome. Greg Maddux is the all-time leader in the figure. Moyer is third behind Maddux and Tom Glavine, so turns out the switching leagues thing didn’t mean as much as I thought it would.
Parker didn’t calculate the stat for Randy Johnson, but using his method I counted Johnson as having faced 1,367 of the 15,855 hitters in Major League history, some 40 shy of Moyer and good for 8.6% (Moyer has actually faced 8.9%).