New Zealand will be without their star man and skipper Kane Williamson for the three-match T20I series against Sri Lanka, that begins on September 1 in Pallekele following the conclusion of the Test series.The selectors have opted to rest Williamson and seamer Trent Boult with Tim Southee named captain. Southee played just a solitary ODI in the World Cup but returned to the playing XI for the first Test recently that his side lost.