Favorite Teams leagues are not included in Single-Season records. Records only remain for 10 seasons.
Single-Season Leaders (Losses)
Average
OBP
SLG
OPS
At Bats
Runs
Hits
Doubles
Triples
Homers
RBIs
Walks
Strikeouts
Stolen Bases
Caught Stealing
Sac Hits
Sac Fly
HBP
GIDP
D+/-
Wins
Losses
ERA
WHIP
Innings
Hits Allowed
HR Allowed
Walks (P)
Strikeouts (p)
Complete Games
Saves
Blown Saves
Shutouts
Quality Starts
Wild Pitches
Hit Batters
H/9
BB/9
SO/9
| 1. | Keuchel, Dallas | (yoshuap) | Wimbourne Wasps | 32 |
| 2. | Loaiza, Esteban | (jsirota) | Saskatchewan Bootleggers | 32 |
| 3. | Leake, Mike | (RitzCards2) | Saddam's WMDs III | 31 |
| 4. | Hernandez, Felix | (gt049) | Vanden Vikings | 31 |
| 5. | Foreman, Frank | Long Beach Sharks | 30 | |
| 6. | Verlander, Justin | (bwoodcoc) | Sarnia Stingers | 30 |
| 7. | Neagle, Denny | (Bears19) | St Louis Cardinals | 30 |
| 8. | Cueto, Johnny | (yoshuap) | Wimbourne Wasps | 30 |
| 9. | Benes, Andy | (filler) | San Bernardino Livewires | 30 |
| 10. | Iwakuma, Hisashi | (tda81) | The Dangerous Alliance | 29 |
| 11. | Hernandez, Felix | (richgibson) | Boston LIBERATORS | 29 |
| 12. | Pettitte, Andy | (kds4316) | Florida Dogs | 29 |
| 13. | Jenkins, Fergie | Biss Boosters | 29 | |
| 14. | Chandler, Spud | (romanticjer) | Forest Hill-toppers | 29 |
| 15. | Harvey, Matt | (nathaniel20) | Albany Crabs 1-260 | 29 |
| 16. | Hahn, Noodles | (billyconn) | Daytona Sunrise | 29 |
| 17. | Feller, Bob | (Kaline6) | Canton Studs | 29 |
| 18. | Young, Chris | (roxrule) | Sault Greyhounds | 29 |
| 19. | Carpenter, Chris | (billyconn) | Aviano Atoms | 29 |
| 20. | Neagle, Denny | (elvistcb49) | Springfield Base Pros | 29 |
| 21. | Clemens, Roger | (Cubsfan3) | O Street Drunks | 29 |
| 22. | Gura, Larry | (griz1962) | Happy Helloween | 28 |
| 23. | Perez, Melido | (boomba) | Albuquerque Blue Crystals | 28 |
| 24. | Anderson, Brett | (yoshuap) | Wimbourne Wasps | 28 |
| 25. | Porcello, Rick | (Itchy008) | Toronto Hornets | 28 |
| 26. | Maddux, Greg | (kingmidas1261) | Houston Colt .45's | 28 |
| 27. | Morris, Ed | (MLBNation) | Gas City Green Sox | 28 |
| 28. | Lonborg, Jim | (Gibblets1973) | Los Gibbletos 18ighteen | 28 |
| 29. | Mulder, Mark | (filler) | San Francisco Giants | 28 |
| 30. | Taylor, Jack | (paddedroom) | TU CHHS 127 | 28 |
| 31. | Scott, Mike | (fps1956) | Stinky Bums | 28 |
| 32. | Kaat, Jim | Kansas City Monarchs | 28 | |
| 33. | Phillippe, Deacon | (Lostit) | Chicago's Lost Orphans | 28 |
| 34. | Bunning, Jim | (toddmkratzer) | Vernon Hills Sox | 28 |
| 35. | Arrieta, Jake | (yoshuap) | Wimbourne Wasps | 28 |
| 36. | Newhouser, Hal | Battle Creek Idiots | 28 | |
| 37. | Foreman, Frank | (Jason1216) | Ashtabula Warriors | 28 |
| 38. | Bender, Chief | (richgibson) | Boston LIBERATORS | 28 |
| 39. | Hurst, Bruce | Sand Hill Road Zoo | 28 | |
| 40. | Dinneen, Bill | Stumptown Floods | 28 | |
| 41. | Tewksbury, Bob | (Lester) | Tuscaloosa CannabisGrowers | 28 |
| 42. | Lima, Jose | (Bj99) | New York Highlanders | 28 |
| 43. | Nagy, Charles | (Bj99) | New York Highlanders | 28 |
| 44. | Viola, Frank | (filler) | San Bernardino Livewires | 27 |
| 45. | Hoyt, La Marr | (Twmart2212) | Belington Wahoos | 27 |
| 46. | Shocker, Urban | (filler) | Burnt Weeny Sandwich | 27 |
| 47. | Rudolph, Dick | (Tsnets) | Boro Jokers | 27 |
| 48. | Morris, Jack | (noodles66) | Savannah Sharks | 27 |
| 49. | Hamels, Cole | (doittoitlars) | Alton Raptors | 27 |
| 50. | Carlton, Steve | (Consigliere33) | Chicago Cubs | 27 |