In response, CD started promisingly, with Mahela Jayawardene continuing his stunning performances for the Stags.
In his eight innings over two seasons for the province, Jayawardene has reached fifty six times, for an average of 62.
He blasted 64 from 36 balls in a classy knock, and survived a bizarre moment along the way. Having played and missed to Kuggeleijn, wicket-keeper Tim Seifert hoisted a half-hearted appeal, to which umpire Billy Bowden went to raise his finger, only to seemingly change his mind halfway through and readjust his hat instead.
However, Santner claimed the key wicket of the Sri Lankan opener, and when George Worker fell soon after the Stags double-digit run rate stalled.
Tom Bruce showed his brute strength in patches as he made 22 from 18 balls, with ND requiring a superb team effort on the boundary to dismiss him - Mitchell claiming a catch on the rope and tossing it to Santner just before he fell out of play.
Bruce averages 45 in the T20 format at a rapid strike rate of 156, and should be in the BlackCaps Twenty20 squad to play Bangladesh in the New Year.
Will Young (31 from 25) and Josh Clarkson (37 not out from 16) provided some late hope for the Stags, but the international-laden Knights bowling attack held steady at the end to pick up their second win of the tournament and keep their playoff hopes alive.
CD remain in second on the ladder, behind leaders Auckland who are in action tomorrow against Wellington.