"I'm no gemerakop but I was thinking of the same thing." (source)

"Rashi gives us the answer, based on the gemara, but let us look at the gemara and see it there. If you perceived this difficulty upon learning the mishna, then you should congratulate yourself - you are developng a 'gemara kop' (Yiddish - a head for gemara). If not, don't worry, just keep learning." (source)