Very weird situation over there. Some Canucks insiders were saying it was a shoulder injury but a couple others came out and said he "needs time to reset," which if i had to guess is likely being fed to them right from the Canucks front office as a way to try and deter digging into the story.
More ominously, a couple hours before this story broke, a guy on the Canucks reddit posted a thread in which he said he was close friends with people in JT's inner circle/family and told the fans to "prepare" for a story to come out about how Miller was taking a leave of absence and to keep him in their thoughts. A couple of the subreddit regulars started digging into his post history and they found multiple references of him saying Miller was recently diagnosed with a degenerative disorder in his neck/spinal area and was trying to combat it with medicine (not painkillers as far as i could read) to stay on the ice a few weeks prior. He apparently revealed Miller's wife also just became a stem cell donor very recently.
Sure enough, within about 2 hours of this guy making that post, the Canucks dropped this and that dude deleted his account.
I'm no expert. but "needing a reset" would check out for a guy who may or may not have just found out his career is over if that claim has any legs. Hope he's alright regardless.
Edit: Someone used the reddit undeleter app thing to go and get a screenshot of the post.