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| Single-Season Losses Leaderboard | |
| * - Indicates Hall of Fame |
| Rank | Player | Losses | IP | Year | Career Leaderboard |
| 1. | Walton Butterfield | 26 | 201.3 | 2020 | |
| 2. | William Depaz | 25 | 184.7 | 2013 | |
| 3. | Robert Marconi | 24 | 177.3 | 2018 | |
| Aaron Cook | 24 | 221.7 | 2014 | ||
| Joseph Kissel | 24 | 192.0 | 2014 | ||
| 6. | Tyler Pelland | 23 | 219.3 | 2010 | |
| 7. | Herman Yutzy | 22 | 202.3 | 2019 | |
| Daryl Salls | 22 | 186.0 | 2016 | ||
| Horacio Ramirez | 22 | 222.7 | 2012 | ||
| Miguel Batista | 22 | 210.7 | 2005 | ||
| 11. | Howard Kapp | 21 | 221.0 | 2019 | |
| Albert Zurita | 21 | 176.0 | 2019 | ||
| Carl Hiles | 21 | 198.0 | 2018 | ||
| Robert Benton | 21 | 120.7 | 2013 | ||
| Aaron Harang | 21 | 174.3 | 2011 | ||
| Mike Esposito | 21 | 204.7 | 2009 | ||
| Chad Billingsley | 21 | 177.7 | 2009 | ||
| Kyle Lohse | 21 | 199.7 | 2007 | ||
| Chin-Hui Tsao | 21 | 193.7 | 2006 | ||
| 20. | Fred McCree | 20 | 202.3 | 2022 | |
| Juan Cain | 20 | 212.0 | 2021 | ||
| Derrick Logan | 20 | 184.7 | 2021 | ||
| Michael Rankin | 20 | 204.0 | 2020 | ||
| Albert Zurita | 20 | 170.3 | 2020 | ||
| Cecil Salas | 20 | 204.0 | 2018 | ||
| Daniel Ramirez | 20 | 203.7 | 2018 | ||
| Dustin McGowan | 20 | 169.7 | 2017 | ||
| Galen Merrick | 20 | 224.7 | 2015 | ||
| Pedro Cuevas | 20 | 211.3 | 2015 | ||
| Tomo Ohka | 20 | 202.0 | 2014 | ||
| Jesse Foppert | 20 | 216.3 | 2013 | ||
| Misao Tsurayaki | 20 | 220.0 | 2012 | ||
| Matt Lorenzo | 20 | 196.0 | 2012 | ||
| Jason Jennings | 20 | 241.0 | 2006 | ||
| 35. | David Martinez | 19 | 274.7 | 2022 | |
| Jeremy Ronquillo | 19 | 226.3 | 2022 | ||
| Juan Moler | 19 | 193.0 | 2021 | ||
| Daniel Ramirez | 19 | 163.3 | 2021 | ||
| Oscar Devries | 19 | 147.3 | 2019 | ||
| Paul Ferreri | 19 | 202.7 | 2018 | ||
| Juan Cain | 19 | 192.0 | 2018 | ||
| Michael Boyer | 19 | 171.7 | 2018 | ||
| Fred McCree | 19 | 182.7 | 2017 | ||
| Floyd Caballero | 19 | 174.3 | 2017 | ||
| Robert Awad | 19 | 230.0 | 2016 | ||
| Matt Cain | 19 | 212.3 | 2016 | ||
| Joseph Kissel | 19 | 160.3 | 2013 | ||
| Jeff Allison | 19 | 204.3 | 2012 | ||
| Brad Penny | 19 | 201.3 | 2010 | ||
| Joel Hanrahan | 19 | 213.7 | 2009 | ||
| Mark Redman | 19 | 197.3 | 2009 | ||
| Woody Williams | 19 | 202.0 | 2004 | ||
| 53. | Dudley Johnson | 18 | 205.7 | 2022 | |
| John Moore | 18 | 220.7 | 2021 | ||
| Jeremy Ronquillo | 18 | 220.0 | 2021 | ||
| Felix Hernandez | 18 | 144.7 | 2021 | ||
| Samuel Servantes | 18 | 201.0 | 2020 | ||
| Billy Evans | 18 | 183.7 | 2020 | ||
| Celestino Alvarez | 18 | 172.7 | 2020 | ||
| Mike Hinkley | 18 | 149.0 | 2019 | ||
| Christian Lundell | 18 | 103.3 | 2018 | ||
| Clint Everts | 18 | 188.3 | 2017 | ||
| Marcos Urbano | 18 | 179.0 | 2017 | ||
| Christian Lundell | 18 | 179.7 | 2016 | ||
| Boof Bonser | 18 | 159.3 | 2016 | ||
| Chris Young | 18 | 189.3 | 2015 | ||
| Matt Cain | 18 | 180.3 | 2015 | ||
| Francis Beltran | 18 | 162.3 | 2015 | ||
| Felton Allen | 18 | 207.7 | 2014 | ||
| Matt Cain | 18 | 190.3 | 2014 | ||
| Horacio Ramirez | 18 | 208.3 | 2013 | ||
| Chadd Blasko | 18 | 156.0 | 2012 | ||
| Ben Howard | 18 | 193.7 | 2011 | ||
| Matt Cain | 18 | 225.0 | 2010 | ||
| Miguel Asencio | 18 | 215.0 | 2010 | ||
| Glendon Rusch | 18 | 196.7 | 2010 | ||
| Travis Blackley | 18 | 240.0 | 2009 | ||
| Kerry Wood | 18 | 229.7 | 2009 | ||
| Nadimu Haruki | 18 | 206.7 | 2009 | ||
| Ian Oquendo | 18 | 203.7 | 2009 | ||
| Brian Lawrence | 18 | 200.3 | 2008 | ||
| Lance Cormier | 18 | 165.0 | 2008 | ||
| Joel Pineiro | 18 | 222.0 | 2007 | ||
| Kerry Wood | 18 | 206.0 | 2007 | ||
| Livan Hernandez | 18 | 186.0 | 2006 | ||
| Danny Haren | 18 | 166.3 | 2006 | ||
| Jorge Depaula | 18 | 141.3 | 2005 | ||
| 88. | Martin Straub | 17 | 231.3 | 2022 | |
| Wilmer Heywood | 17 | 205.7 | 2022 | ||
| Juan Moler | 17 | 166.7 | 2022 | ||
| Jeffery Oliveros | 17 | 212.3 | 2021 | ||
| Elliott Knowles | 17 | 200.3 | 2021 | ||
| Justin Phillips | 17 | 183.7 | 2021 | ||
| Faustino Fusco | 17 | 221.3 | 2020 | ||
| Juan Moler | 17 | 211.7 | 2020 | ||
| Robert Falcone | 17 | 177.7 | 2020 | ||
| Daniel Ramirez | 17 | 208.3 | 2019 | ||
| Anthony Rikyu | 17 | 192.7 | 2019 | ||
| Carl Hiles | 17 | 110.7 | 2019 | ||
| Glen Rakestraw | 17 | 195.7 | 2018 |
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