Celtics boss Danny Ainge likes toughness in his players. Despite not having an Arnold Schwarzenegger physique, he was pretty tough on the court and backed down from nobody. In the 2014 NBA draft, Ainge drafted for toughness taking Tony Allen and Delonte West in the first round. Allen is a one-time NBA Champion (2008 with Celtics) and is in his 14th NBA season. He has rightfully earned the reputation as a dogged, tough defender.
West played a number of seasons in the League and was always a time bomb ready to explode.