Dialogue doesn't make sense sometime, but I don't think is the TL fault.
MC says how can she be so bad after all that baseball.
From what we see the brother made her run around to burn fat, not practice the whole game, but then again, he called her with the nickname she dislike so to get a ball thrown in his direction that could get the bully, and she did exactly that, only judging his position from the voice, I think that is pro-level.