It does say in the article that they gave it the off season to settle down but at the end of the first week back it was decided to do something. They started pre-season on the 5th November - 3 months ago.
If he had the operation then - just before he went home for Christmas, it seems a decent timeline for recovery. It reads as if he HASN'T just had it done. If it was done in November then that seems reasonable to me. The must have had medical advice to give it the off season to heal itself. I agree though it is a shame to lose him at the start but I am used to it with Kearney as he has always been injury prone. Gaskell for me at fullback.