I would love to hear a fuller story on what it took for Petra to come back. It think it's easy to underplay it because her results have been good since then, even right away, so we infer that it wasn't all that difficult. She has talked about the racket feeling totally different in her hand, which must have been scary and technically hard to adjust to. She couldn't make a fist - so grip her racket totally - when she came back and that lasted for a while and still might be the case. She has also mentioned that it hurt that people didn't think she could come back. There are a bunch of layers of trauma that we never see. I think it's remarkable and I'd love to hear the whole story.
She is lucky that the knife missed the nerves, I believe.