I don't know how Greg got injured or exactly what play(s) resulted in the injury. However, I did see him appear to be in pain after his dive-for-the-pylon TD.
Below are two of my photos of the play. It doesn't look like a play that would result in an injury, but watching him after the play, it was clear that he was in pain. He landed hard on his stomach and lay there for a moment. He rolled over and started to get up but then he knelt down on his hands and knees. He looked like he might have had the wind knocked out of him, though now we know that something else was seriously wrong.
After a minute or two he got up and went to the sidelines. After that, I noticed that he wasn't in the lineup on every series, but I thought it was because the coaches were rotating Hines in to give Greg a breather. When he was in the lineup he still played great, which is amazing considering what we know now. I join everyone else in wishing him a speedy and full recovery. I think he is the most exciting player to play for Wake since Michael Campanaro.