| Career - Worst ERA | |||
| Rk | Player Name | Totals | |
| 1 | Chan Ho Park | 5.23 | |
| 2 | Tom Milone | 5.13 | |
| 3 | Scott Erickson | 5.11 | |
| 4 | Matt Morris | 5.07 | |
| 5 | Al Leiter | 5.03 | |
| 6 | Ramon Martinez | 4.95 | |
| 7 | Francisco Liriano | 4.74 | |
| 8 | Tom Glavine | 4.73 | |
| 9 | Trevor Wilson | 4.69 | |
| 10 | Mark Prior | 4.68 | |
| 11 | Chris Bassitt | 4.55 | |
| 12 | Joe Musgrove | 4.54 | |
| 13 | Jorge De La Rosa | 4.48 | |
| 14 | Ubaldo Jimenez | 4.46 | |
| 15 | Pete Schourek | 4.43 | |
| 16 | Cole Hamels | 4.37 | |
| 17 | Hisashi Iwakuma | 4.35 | |
| 18 | JOSE RIJO | 4.30 | |
| 19 | Max Fried | 4.14 | |
| 20 | Matt Cain | 4.13 | |
| 21 | Antonio Senzatela | 4.08 | |
| 22 | Andy Pettitte | 3.92 | |
| 23 | Mike Minor | 3.84 | |
| 24 | Mark Buehrle | 3.81 | |
| 25 | Jim Abbott | 3.79 | |
| Single Season - Worst ERA | |||||
| Rk | Player Name | Totals | Year | ||
| 1 | Trevor Wilson | 7.94 | 1994 | ||
| 2 | Al Leiter | 7.26 | 2000 | ||
| 3 | Matt Morris | 6.83 | 2007 | ||
| 4 | Jeff Ballard | 6.64 | 1990 | ||
| 5 | Micah Owings | 6.55 | 2009 | ||
| 6 | Pete Schourek | 6.29 | 1997 | ||
| 7 | Matt Morris | 6.23 | 2005 | ||
| 8 | Cole Hamels | 6.21 | 2007 | ||
| 9 | Matt Cain | 6.18 | 2015 | ||
| 10 | JOSE RIJO | 6.13 | 1990 | ||
| 11 | Miguel Batista | 5.91 | 2004 | ||
| 12 | Mark Prior | 5.91 | 2005 | ||
| 13 | Al Leiter | 5.81 | 2002 | ||
| 14 | Mike Sirotka | 5.74 | 2000 | ||
| 15 | Greg Hibbard | 5.69 | 1991 | ||
| 16 | Chan Ho Park | 5.53 | 1999 | ||
| 17 | Braxton Garrett | 5.50 | 2023 | ||
| 18 | Scott Erickson | 5.42 | 1997 | ||
| 19 | Shawn Hill | 5.41 | 2008 | ||
| 20 | Angel Miranda | 5.36 | 1994 | ||
| 21 | Alex Young | 5.36 | 2020 | ||
| 22 | Ron Darling | 5.34 | 1990 | ||
| 23 | Matt Morris | 5.28 | 2004 | ||
| 24 | Andrew Albers | 5.27 | 2017 | ||
| 25 | Charlie Leibrandt | 5.25 | 1991 | ||