I honestly don't know what the deal is. I do know it's not illness and don't believe it's concussion. He's listed as undisclosed injury. Concussion is usually listed as upper body.
https://letsgodu.com/2019/01/28/fighting-hawks-fans-begin-annual-trek-to-denver/#more-671
Seems like ever since they legalized the weed, the effort has been a little weak. Coincidence?