I am looking for an idiom to use for a person (player, employee etc.) that proves more talented than expected. In my native language, I often hear in sports being something that literally translates to "season revelation", but I have sometimes used it (informally) for junior colleagues.
A "season revelation" is:
- typically (very) young
- talented at what it does, but few know about this until "revealed"
- a one-time event in one's life (cannot be "revealed" more than once)
"Rising star" comes into my mind, but I am not sure if it grasps the same meaning.