As we have seen over the years with Morneau, Mauer, Buxton, etc, one thing that we know for sure about post-concussion symptoms is that they are wildly unpredictable. I think if we were still in the regular season, Buxton wouldn't have played yesterday even if he wasn't showing any symptoms. Teams these days typically like to put a guy through a workout and see how he's feeling the next day before they fully clear him, and this situation is a good example of why. Sometimes the symptoms are triggered by the previous day's workout.