I'd initially thought the he pulled a glute or hamstring when seeing the injury last year.
It appears that it's a knee injury and he's still recovering from it. It's close to a year ago now. Perhaps he is simply being extra cautious but he's been out other game for ages now.
Really feel sorry for him but at this point we have to wonder if it's time to start excluding him from the conversation because we don't know when he'll be back and how long it will take him to find form once he does return.