His audio interview also is finally up, there are a few more details:
He clearly says the knee was not an issue. He just asked the physio to compress it a little bit for a few games in order to feel better, but it was not the reason for his bad match.
Nothing was really working in his game, FH, BH, serve...
The journalist tells him that everybody was surprised because he usually delivers in Slams and that he looks a bit surprised himself by his bad performance. He agrees and says he will have to draw a lot of conclusions from this non-match. It had nothing to do with the fact he was playing for the first time in that big stadion in his opinion.
And when he's asked about Fish, he doesn't give him so much credit, but rightly so imo.
He says Fish played a solid match, nothing more. Gaël's shots were so short, he was not serving well, he was gifting him so many points and let him completely dominate.