| Career - Worst ERA | |||
| Rk | Player Name | Totals | |
| 1 | Ron Darling | 7.24 | |
| 2 | Nathan Eovaldi | 5.52 | |
| 3 | Jose Quintana | 5.41 | |
| 4 | Ricky Bones | 5.35 | |
| 5 | Todd Stottlemyre | 5.34 | |
| 6 | Jason Schmidt | 5.21 | |
| 7 | Rick Porcello | 5.05 | |
| 8 | Jon Lieber | 5.04 | |
| 9 | Greg Maddux | 4.92 | |
| 10 | Kent Bottenfield | 4.84 | |
| 11 | Wilson Alvarez | 4.79 | |
| 12 | Tyler Mahle | 4.75 | |
| 13 | Jason Hammel | 4.69 | |
| 14 | Lucas Giolito | 4.67 | |
| 15 | German Marquez | 4.66 | |
| 16 | Brandon McCarthy | 4.65 | |
| 17 | Jaime Navarro | 4.61 | |
| 18 | Frank Viola | 4.61 | |
| 19 | Daisuke Matsuzaka | 4.61 | |
| 20 | Dan Haren | 4.43 | |
| 21 | Freddy Garcia | 4.42 | |
| 22 | Javier Vazquez | 4.37 | |
| 23 | James Shields | 4.32 | |
| 24 | Barry Zito | 4.28 | |
| 25 | Clayton Kershaw | 4.18 | |
| Single Season - Worst ERA | |||||
| Rk | Player Name | Totals | Year | ||
| 1 | Frank Viola | 8.41 | 1994 | ||
| 2 | Ron Darling | 7.70 | 1994 | ||
| 3 | Wilson Alvarez | 7.09 | 1994 | ||
| 4 | Jaime Navarro | 6.76 | 1994 | ||
| 5 | Jim Deshaies | 6.49 | 1991 | ||
| 6 | Randy Johnson | 6.35 | 1990 | ||
| 7 | Amaury Telemaco | 6.09 | 1999 | ||
| 8 | Wilson Alvarez | 5.88 | 2000 | ||
| 9 | Javier Vazquez | 5.73 | 2011 | ||
| 10 | Rick Porcello | 5.70 | 2018 | ||
| 11 | Jameson Taillon | 5.69 | 2024 | ||
| 12 | Mike Sirotka | 5.64 | 2001 | ||
| 13 | Brett Tomko | 5.60 | 2006 | ||
| 14 | Lucas Giolito | 5.52 | 2024 | ||
| 15 | Jason Schmidt | 5.51 | 2007 | ||
| 16 | Jose Quintana | 5.51 | 2018 | ||
| 17 | Frank Viola | 5.47 | 1990 | ||
| 18 | C.C. Sabathia | 5.43 | 2005 | ||
| 19 | Todd Stottlemyre | 5.43 | 1997 | ||
| 20 | Yovani Gallardo | 5.33 | 2013 | ||
| 21 | Jason Hammel | 5.30 | 2016 | ||
| 22 | Wilson Alvarez | 5.25 | 1997 | ||
| 23 | Wilson Alvarez | 5.24 | 1999 | ||
| 24 | German Marquez | 5.19 | 2020 | ||
| 25 | Jon Lieber | 5.18 | 1998 | ||