The Celtics coach 's infrequent but clear moments of dissatisfaction can be a driving force .
Brad Stevens ' halftime anger played an important role in their 116 - 96 win over Memphis last night .
The Celtics Brad Stevens 's infrequent but clear moments of dissatisfaction can be a driving force .
Brad Stevens ' halftime anger played an important role in their 116 - 96 win over Memphis last night .