Surgery with recovery time of 2-4 weeks seems pretty minor...like play-through-it-and-wait-for-the-offseason minor.
The word I heard a few weeks ago after he left that game was that he didn't wear his knee brace first time after his "Shane Doan's" injury and his knee "clicked". The prognosis was that he needed a surgery at that time. They might have tried to "patch" it before TD, hard to say ...