I’m afraid I might need a bit more context to be able to help you. Where did you see this sentence?
It may be about a cricket player called Watson and ‘launch’ refers to ‘throwing the ball’.
‘Knocked back’ may refer to some sort of ‘rejection’ or ‘shock’, but I can’t be sure without a context. I may be completely wrong as well 🙂
I would appreciate any help with this from other members too.