defatigable: capable of being wearied or tired out; easily tired or wearied
ANTONYM: indefatigable; tireless
Example: Thus the mantle of leadership fell on the quiet and unassuming but defatigable Senaka Bandara - line out specialist and a hard player on the loose. [Reference: Kandy SC favoured to win Caltex League rugby title, http://www.sundayobserver.lk/2011/08/14/spo02.asp]
ANTONYM: indefatigable; tireless
Example: Thus the mantle of leadership fell on the quiet and unassuming but defatigable Senaka Bandara - line out specialist and a hard player on the loose. [Reference: Kandy SC favoured to win Caltex League rugby title, http://www.sundayobserver.lk/2011/08/14/spo02.asp]