<Tr> <Th> </Th> <Td> 2.02 </Td> <Td> Jack Pfiester </Td> <Td> Pittsburgh (NL), Chicago (NL) </Td> <Td> 1903--04, 1906--11 </Td> </Tr> <Tr> <Th> 5 </Th> <Td> 2.03 </Td> <Td> Smoky Joe Wood </Td> <Td> Boston (AL), Cleveland (AL) </Td> <Td> 1908--15, 1917--22 </Td> </Tr> <P> Because of rules changes post-1920, most notably the abolition of the spitball and frequent replacement of soiled or scuffed baseballs, the increased importance of the home run (largely due to Babe Ruth), and the American League's adoption of the designated hitter rule, ERAs have been noticeably higher than in the early decades of the sport . </P> <P> This is a list of the lowest ERAs among pitchers that played their entire careers after 1920 (minimum 1,000 innings pitched). Note that three of the top six (Clayton Kershaw, Whitey Ford and Sandy Koufax) were primarily starting pitchers . Hoyt Wilhelm was a reliever for most of his career, while the other two are closers . </P>

What is considered a good era in mlb