Bert Blyleven had a 2.39 BB/9 and a 6.70 K/9 in his career. That’s 1,322 walks and 3,701 strikeouts in 4,970 innings pitched. Note that when he retired, he was third all-time on the strikeouts list behind Steve Carlton and Nolan Ryan (Roger Clemens and Randy Johnson passed him afterward).
Four players in history have pitched more than 4,900 innings and had a BB/9 under 3 and a K/9 over 6. Roger Clemens, Don Sutton, Bert Blyleven and Greg Maddux. If you relax the standards to 4,700 innings, Tom Seaver joins; to 4,500, Ferguson Jenkins is in. Maddux will definitely be a first ballot Hall of Famer and Clemens would be if not for off-the-field issues, so why isn’t Bert?
*Also note that I use these stats because a pitcher has total control over how many walks and strikeouts he gives up, while everything else is dependent on fielding. He also has some control over home runs and ground balls, too, but I’ll talk about that at a later time.