Gayle chased a tricky total of 259 .
Gayle scored an unbeaten century ( 133 * off 135 balls ) which proved decisive as the Windies beat South Africa in the knockout encounter .
Chasing a tricky total of 259 , Gayle scored an unbeaten century ( 133 * off 135 balls ) which proved decisive as the Windies beat South Africa in the knockout encounter .