Age limits in elite sport are usually defended as safeguards: because young athletes are vulnerable, institutions may restrict their access to senior competition. This short philosophical note argues that the justification is more complicated. Chronological age is a useful administrative proxy, but it often compresses three distinct questions into one number: whether an athlete can perform at senior level, whether she can exercise decision-making autonomy, and whether she remains vulnerable to exploitation. These properties can come apart. The case of Chinese javelin thrower Yan Ziyi makes the distinction unusually vivid. After turning eighteen in May 2026, Yan threw 71.74 metres and, by July, had won four Diamond League meetings. Her case does not show that age rules are unjustified, nor that exceptional performance proves full autonomy. It shows instead that protection and recognition are non-substitutable moral tasks. Sport may have reasons to protect a young person without thereby having sufficient reason to deny the standing of her demonstrated performance. I propose a principle of threshold paternalism: age-based restrictions are defensible as presumptions, but the burden of justification rises when a rule withholds a major opportunity from an athlete whose relevant competitive capacity is already established.