Since then , Jeff has sustained four separate concussions , including one at the beginning of the 2014 - 15 season from which he returned eyebrow - raisingly quickly .
Is the likely culprit behind Jeff 's lackluster season .
Since then , Jeff has sustained four separate concussions , including one at the beginning of the 2014 - 15 season from which he returned eyebrow - raisingly quickly and is the likely culprit behind his lackluster season .