To rattle somebody can mean to behave towards someone in order to make them lose their composure or gain a psychological edge over them. That's why in social situations the word is commonly used in connection with sport. In a professional setting, you may want to rattle somebody if you are in competition with them, or if you want to test their character. A related expression is to 'rattle someone's cage.' To 'rattle' means to shake something in order to make noise. As a noun, a 'rattle' refers to a toy often given to babies.

1. Don't let what Peter said get under your skin. He's just trying to rattle you!
2. Our tough tackling was rattling the opposition, and stopped them playing their usual game.

1. I didn't expect the line of questioning in the job interview to be so aggressive. It really rattled me and it showed in my performance.
2. Briefly losing my place during my speech at the conference was embarrassing, but I didn't let it rattle me.