For single seasons, From 1901 to 2008, (requiring SV≥50), sorted by smallest ERAp

  Cnt Player            **ERA ** SV Year Age Tm  Lg  G  GS CG SHO GF  W  L  W-L%   IP   H   R   ER  BB  SO   ERA  HR  BF   AB  2B 3B IBB HBP  SH  SF GDP  SB CS Pk BK WP   BA   OBP   SLG   OPS  OPS   Pit  Str
 ----+-----------------+--------+--+----+---+---+--+---+--+--+---+--+--+--+-----+-----+---+---+---+---+---+------+--+----+----+--+--+---+---+---+---+---+---+--+--+--+--+-----+-----+-----+-----+----+----+---- 
    1 Randy Myers          128   53 1993  30 CHC NL  73  0  0   0 69  2  4  .333  75.1  65  26  26  26  86   3.11  7  313  283 15  1   2   1   1   2   8   1  1  0  0  3  .230  .295  .364  .659   83           
    2 John Smoltz          128   55 2002  35 ATL NL  75  0  0   0 68  3  2  .600  80.1  59  30  29  24  85   3.25  4  314  287 12  2   1   0   2   1   9   2  1  0  1  1  .206  .266  .303  .569   52 1169  793 
    3 Rod Beck             144   51 1998  29 CHC NL  81  0  0   0 70  3  4  .429  80.1  86  33  27  20  81   3.02 11  349  320 14  3   4   2   2   5   3   8  1  0  0  2  .269  .311  .434  .745   97           
    4 Mariano Rivera       191   50 2001  31 NYY AL  71  0  0   0 66  4  6  .400  80.2  61  24  21  12  83   2.34  5  310  292  4  0   2   1   4   1   5   3  3  0  0  1  .209  .242  .274  .516   34 1160  836 
    5 Eric Gagne           192   52 2002  26 LAD NL  77  0  0   0 68  4  1  .800  82.1  55  18  18  16 114   1.97  6  314  291 11  2   4   2   3   2   4   2  3  0  0  1  .189  .235  .302  .537   49 1235  864 
    6 Dennis Eckersley     196   51 1992  37 OAK AL  69  0  0   0 65  7  1  .875  80    62  17  17  11  93   1.91  5  309  294 11  1   6   1   3   0   3   9  1  0  0  0  .211  .242  .306  .548   57           
    7 Bobby Thigpen        210   57 1990  26 CHW AL  77  0  0   0 73  4  6  .400  88.2  60  20  18  32  70   1.83  5  347  307  8  2   3   1   4   3  12   3  0  0  0  2  .195  .271  .283  .554   56           
    8 Mariano Rivera       231   53 2004  34 NYY AL  74  0  0   0 69  4  2  .667  78.2  65  17  17  20  66   1.94  3  316  289  7  0   3   5   2   0  11   5  1  0  0  0  .225  .287  .280  .567   50 1141  781 
    9 Trevor Hoffman       263   53 1998  30 SDP NL  66  0  0   0 61  4  2  .667  73    41  12  12  21  86   1.48  2  274  249  6  2   2   1   3   0   7   7  0  0  0  8  .165  .232  .229  .461   30           
   10 Eric Gagne           335   55 2003  27 LAD NL  77  0  0   0 67  2  3  .400  82.1  37  12  11  20 137   1.20  2  306  279  6  0   2   3   4   0   0   2  1  0  0  2  .133  .199  .176  .375    4 1187  824 

Seasons/Careers found: 10.

 Photos from the George Grantham Bain Collection at the Library of Congress.