A baseball star wrote "kick me" on a boy's back after the 10-year-old asked him to autograph his shirt.
Milwaukee Brewers pitcher Curtis Leskanic was making a good will visit to Clinton Middle School in Wisconsin.
But the player left Brett Larson upset and bruised when his classmates took the message literally.
Brett, who later asked a friend what Leskanic wrote, said: "This one kid - I don't know if he's really my friend - he kicked me really hard in the knee".
His angry mum, Lisa, wrote a letter of complaint to the Milwaukee Brewers, which she claims they did not respond to.
She also contacted the Milwaukee Journal Sentinel and a lawyer, who said that Leskanic did nothing wrong legally.
Lynn Sprangers, spokeswoman for the Brewers, said they could not find the letter and offered to give Brett a new shirt.
In Leskanic's defence, she said: "He was signing autographs until he almost couldn't write anymore. Curtis is a fun-loving and kind of spontaneous guy. Middle school kids are kind of rambunctious. I think Curtis was just having some fun".