Do not fight the habit that already works
If a player already reflects in a familiar channel, keep that front door at first. Ask for a short pattern: load, body, what worked, what was hard, one lesson, and one carry-forward point.
Make the reflection visibly useful
Young players do not care about data quality. They care whether the team listens and whether the reflection changes tomorrow's training. Respond to strong observations and connect them to the weekly focus.
Professional, not administrative
Logging should feel like building a tennis brain, not completing homework. Start with a two-week pilot, review which prompts add value, and remove anything that does not improve learning or decisions.