ERA
Zack Kelly · Season-by-season history
ERA over time
- Boston Red Sox · MLB
Hover over a bar for its value. Only numeric values with a recorded season are charted; missing seasons are not treated as zero.
| Season | Team | League | ERA |
|---|---|---|---|
| 2025 |  Boston Red Sox |
MLB | 4.58 |
| 2024 | Boston Red Sox |
MLB | 3.97 |
| 2023 | Boston Red Sox |
MLB | 3.86 |
| 2022 | Boston Red Sox |
MLB | 3.95 |