One of the most common reasons why your velocity may have gone down in season is simply fatigue. There are a wide variety of causes of this fatigue, ranging from insufficient preparation during an offseason The physical demands of a long baseball season can take a toll on a player's body, leading to a decline in performance. This is especially true for pitchers, who place a great deal of stress on their arms every time they throw. Closely related to fatigue, overuse can also lead to decreased velocity. This can occur if a pitcher is throwing too many pitches without adequate rest and recovery time. Additionally, even minor injuries can affect a pitcher's ability to throw at full speed. If a player is dealing with pain or discomfort, they may consciously or unconsciously alter their throwing mechanics to compensate, which can result in a decrease in velocity.
Both to continue positive trends in training and to reduce injury risk and declining performance throughout a season, athletes must make sure to continue to train throughout their seasons. Although on-field training and performance is at the forefront of players’ minds during the season, neglecting training off the field can result in adverse affects on an athlete’s performance and health.
Psychological factors and alterations to movement patterns can often work in tandem throughout a season. If a pitcher is feeling stressed, anxious, or lacking in confidence, this can translate into physical performance, including a decrease in pitching velocity. Additionally, a greater emphasis may be placed by a coach or the player themselves on throwing with improved accuracy (command), which could affect the pitchers ability to throw at a high intensity or could cause mechanical breakdowns. It is often found that changes in a pitcher's mechanics can lead to a decrease in velocity. This can happen intentionally, as when a player modifies their delivery to try to improve control or deception, or unintentionally, as a result of fatigue, bad habits, or coaching advice. Additionally, if players do not continue to monitor their performance and adhere to their corrective drills, they mind themselves reverting back to old habits that were corrected the prior offseason.
If a pitcher doesn't maintain their strength and conditioning during the season, they can lose velocity. It's important for players to continue strength training and conditioning exercises even during the season to maintain their physical abilities. This also includes weight management/maintenance. Many pitchers who made positive changes to their body composition find themselves reverting to old habits or not eating enough while under the stressors that come with the season, such as limited eating windows and limited access to nutrient dense food, extensive travel times, or an increased workload in school.
For these reasons and many others, it's important for players and teams to monitor workload and fatigue levels, maintain proper conditioning, strength, and mechanics, manage injuries appropriately, and support mental health throughout the season. This can help minimize declines in performance, especially pitching velocity.