He still pitched 8 2/3 innings before the "F" rating dropped to F8. For a S5 rated pitcher, I'm surprised HAL didn't dock him a F every complete inning after completing his 6.
I like that the classic "When asked about his strikeout total after the game..." line is given in the summary capsule, but the fact that Duren struck out 21 was actually never mentioned in either the headline or the article. These reporters are getting sloppy, I tell ya...