I have traveled around the world since I was a child, and I have never seen anyone bring tennis rackets onboard. When I travel for an important meeting or event, I travel the day before, at least. And if I have to bring something onboard the aircraft with me other than what I know is an acceptable item, I call reservations and ask. And nowadays I get onboard as soon as I can if I have something with me that MUST be stored in the overhead bin.