Hi Naomi,
Iโm 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 โlaunchโ refers to โthrowing the ballโ.
โKnocked backโ may refer to some sort of โrejectionโ or โshockโ, but I canโt be sure without a context. I may be completely wrong as well ๐
I would appreciate any help with this from other members too.