system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What use are coaches of top tier athletes like Federer or Tiger Woods?

What can the coach say or do to improve their game?
gpt
You don't always need to be better than someone (do you think Coach K at Duke can beat any of his players 1 on 1) at a sport to coach them, you observe them to see flaws in their game (amateurs watching TV--especially with slow motion replays can usually spot areas that require improvement).  

Also, a coach can focus on competition reconnaissance and strategy, allowing the athlete to focus purely on practice.