Do "player" and "perfomer" in "no mean player" and "no mean performer" have to be a sport player or performer like an actor and singer, or just anyone that does some activity?
Performer means: An entertainer who performs a dramatic or musical work for an audience. A player can be a performer but not vice-versa. A player is a person who participates in or is skilled at some game, he can be a performer or an important participant (as in a business deal)
Generally “no mean feat” means: something not at all easy to do. "No mean player" means a great player who can not be beaten or defeated easily.