The book that I am reading is called the eyes of the killer robot
by John Bellairs.
It is about a little kid living with his grandparents and having a professor as a best friend.
one day this professor takes him to a baseball court and tells him that his grandpa used to play there and an inventor also in this court was making and selling useless stuff that nobody wanted. One day this inventor made a robot that could automatically throw balls for training the team found it well to purchase but his grandparent told the team not to buy the robot because he did not like his eyes, he also said that if they would buy it he would abort the team!
The team did not buy the robot and that made the inventor angry and promised revenge to the grandpa!