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| Single-Season ERA Leaderboard | |
| * - Indicates Hall of Fame |
| Rank | Player | ERA | IP | Year | |
| 1. | Ernesto Mejias | 2.007 | 228.7 | 2008 | |
| 2. | Jack Smith | 2.241 | 237.0 | 2008 | |
| 3. | Robert Welsch | 2.565 | 214.0 | 2009 | |
| 4. | Ernesto Mejias | 2.685 | 248.0 | 2007 | |
| 5. | Jack Smith | 3.024 | 211.3 | 2009 | |
| 6. | Robert Welsch | 3.101 | 238.0 | 2007 | |
| 7. | Adan Gingras | 3.183 | 169.7 | 2007 | |
| 8. | Michael Davis | 3.194 | 242.3 | 2008 | |
| 9. | Ernesto Mejias | 3.254 | 185.3 | 2009 | |
| 10. | Ronnie Nesmith | 3.293 | 205.0 | 2008 | |
| 11. | Robert Welsch | 3.305 | 209.7 | 2008 | |
| 12. | John Moronta | 3.333 | 270.0 | 2009 | |
| 13. | Joshua Grothe | 3.365 | 224.7 | 2007 | |
| 14. | Ronnie Nesmith | 3.370 | 211.0 | 2009 | |
| 15. | Carlos Leal | 3.387 | 186.0 | 2008 | |
| 16. | Patrick Segars | 3.391 | 212.3 | 2009 | |
| 17. | William Tuggle | 3.415 | 195.0 | 2008 | |
| 18. | John Moronta | 3.493 | 257.7 | 2008 | |
| 19. | Wilfredo Erazo | 3.508 | 169.3 | 2009 | |
| 20. | David Jarvis | 3.546 | 223.3 | 2008 | |
| 21. | David Jarvis | 3.551 | 256.0 | 2007 | |
| 22. | Fidel Havana | 3.629 | 186.0 | 2009 | |
| 23. | Kenneth Robinson | 3.667 | 216.0 | 2008 | |
| 24. | Angel Barbosa | 3.744 | 192.3 | 2008 | |
| 25. | John Porter | 3.767 | 272.3 | 2009 | |
| 26. | Adan Gingras | 3.817 | 193.3 | 2009 | |
| 27. | Guillermo Torres | 3.823 | 188.3 | 2007 | |
| 28. | James Barton | 3.869 | 216.3 | 2008 | |
| 29. | Ruben Olmeda | 3.893 | 178.0 | 2007 | |
| 30. | Felix Pedraza | 3.927 | 183.3 | 2008 | |
| 31. | Conrado Amezcua | 3.945 | 175.7 | 2009 | |
| 32. | Jermaine Spates | 3.954 | 211.7 | 2009 | |
| 33. | Paul Therrien | 3.958 | 243.3 | 2009 | |
| 34. | Paul Therrien | 3.961 | 222.7 | 2008 | |
| 35. | Carlos Leal | 4.003 | 220.3 | 2009 | |
| 36. | Henry Ingles | 4.004 | 184.3 | 2007 | |
| 37. | Dillon Crawford | 4.008 | 222.3 | 2007 | |
| 38. | Albert Martineau | 4.017 | 233.0 | 2009 | |
| 39. | John Flora | 4.046 | 211.3 | 2009 | |
| 40. | John Flora | 4.061 | 201.7 | 2007 | |
| 41. | Jermaine Spates | 4.064 | 199.3 | 2008 | |
| 42. | Virgil Haugh | 4.082 | 183.0 | 2007 | |
| 43. | Garret Reyes | 4.096 | 215.3 | 2009 | |
| 44. | Alvin Medina | 4.114 | 175.0 | 2007 | |
| 45. | Fidel Havana | 4.125 | 211.7 | 2008 | |
| 46. | Oswaldo Acuņa | 4.192 | 219.0 | 2007 | |
| 47. | Hector Ferrer | 4.198 | 218.7 | 2008 | |
| 48. | William Tuggle | 4.214 | 230.7 | 2009 | |
| 49. | Telmo Cosenza | 4.227 | 247.0 | 2007 | |
| 50. | John Barrett | 4.263 | 215.3 | 2009 | |
| 51. | Victor McFaddin | 4.265 | 211.0 | 2007 | |
| 52. | James Varnell | 4.306 | 177.7 | 2009 | |
| 53. | Telmo Cosenza | 4.326 | 233.0 | 2008 | |
| 54. | Byron Hernandez | 4.336 | 220.0 | 2008 | |
| 55. | Yong Beller | 4.354 | 204.7 | 2008 | |
| 56. | Paul Therrien | 4.397 | 219.0 | 2007 | |
| 57. | Manny Quijada | 4.406 | 206.3 | 2007 | |
| 58. | Guillermo Torres | 4.406 | 192.0 | 2008 | |
| 59. | Adrian Pastrana | 4.412 | 169.3 | 2007 | |
| 60. | Man Mattia | 4.430 | 215.3 | 2008 | |
| 61. | Bill Inman | 4.447 | 224.7 | 2008 | |
| 62. | Brandon Jarrett | 4.451 | 182.0 | 2007 | |
| 63. | James Barton | 4.452 | 216.3 | 2007 | |
| 64. | Manny Quijada | 4.458 | 216.0 | 2008 | |
| 65. | David Hemphill | 4.463 | 201.7 | 2009 | |
| 66. | David Borges | 4.469 | 193.3 | 2008 | |
| 67. | John Moronta | 4.475 | 239.3 | 2007 | |
| 68. | Higinio Hernandez | 4.476 | 187.0 | 2007 | |
| 69. | Higinio Hernandez | 4.491 | 166.3 | 2009 | |
| 70. | Juan Martinez | 4.500 | 224.0 | 2007 | |
| 71. | Albert Martineau | 4.539 | 190.3 | 2008 | |
| 72. | Stephen Pope | 4.551 | 176.0 | 2007 | |
| 73. | Angel Barbosa | 4.554 | 168.0 | 2007 | |
| 74. | David Jarvis | 4.556 | 213.3 | 2009 | |
| 75. | Yong Beller | 4.559 | 203.3 | 2009 | |
| 76. | Alvin Medina | 4.577 | 194.7 | 2009 | |
| 77. | Guillermo Torres | 4.587 | 206.0 | 2009 | |
| 78. | Hideki Suzuki | 4.600 | 225.0 | 2009 | |
| 79. | David Hemphill | 4.602 | 191.7 | 2008 | |
| 80. | Alvin Medina | 4.606 | 213.0 | 2008 | |
| 81. | Leon Littrell | 4.610 | 164.0 | 2009 | |
| 82. | John Suggs | 4.634 | 213.7 | 2007 | |
| 83. | John Porter | 4.663 | 212.3 | 2008 | |
| 84. | Gregory Micco | 4.687 | 217.0 | 2007 | |
| 85. | Alvaro Ramos | 4.700 | 172.3 | 2007 | |
| 86. | Fredrick Planas | 4.712 | 198.7 | 2009 | |
| 87. | Jim Lenahan | 4.716 | 208.0 | 2009 | |
| 88. | Francisco Graziano | 4.729 | 177.0 | 2008 | |
| 89. | John Flora | 4.729 | 209.3 | 2008 | |
| 90. | Silvio Perez | 4.738 | 233.7 | 2007 | |
| 91. | Daniel Smail | 4.760 | 202.3 | 2009 | |
| 92. | Oscar Moreno | 4.774 | 169.7 | 2007 | |
| 93. | Matthew Sanchez | 4.822 | 214.7 | 2007 | |
| 94. | John Murrin | 4.829 | 164.0 | 2007 | |
| 95. | Brandon Jarrett | 4.917 | 201.3 | 2008 | |
| 96. | Vernon Olguin | 4.918 | 183.0 | 2007 | |
| 97. | David Hemphill | 4.927 | 186.3 | 2007 | |
| 98. | Telmo Cosenza | 4.934 | 200.7 | 2009 | |
| 99. | Victor McFaddin | 4.947 | 218.3 | 2009 | |
| 100. | Yong Beller | 4.951 | 176.3 | 2007 |
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