The all-time leader in this statistic is retired pitcher, Randy Johnson (10.67 SO/9). The only three other players who are have averaged over 10 are active pitchers, Kerry Wood (10.385), Tim Lincecum (10.169), and Pedro Martínez (10.081). Note that the previous statement is based on innings pitched minimums that apply mostly to starting pitchers. For relievers, using 300 career innings pitched or 200 appearances as the minimum. For instance, the record holder is Brad Lidge (RP) who is the all-time leader in strikeouts per nine innings (12.1 K/9) among pitchers with at least 200 appearances in their career.