Put into bat, Knights lost a wicket early after Kane Williamson was scalped by Ravi Rampaul (3-34) for 1 but Anton Devcich, with a run-a-ball 47 and skipper Daniel Flynn (21) resurrected the innings only to lose the plot later.
The duo stitched a 60-run second-wicket partnership to bring the innings back on track before Flynn was caught behind off Sri Lankan off-spinner Dilshan Munaweera (2-10).
The break did not proved good for the Kiwi champions, who saw a run out after Devcich returned to the pavilion and Scott Styris (0) fell to Munaweera's spin in the same over.
But just when the momentum seemed to be shifting in Knights favour after a few lusty hits by Watling, Daryl Mitchell (9) lost his cool against Rampaul to be holed out at long on by James Franklin.
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Rampaul struck again after picking up Watling, as the wicketkeeper-batsman struck 3 fours and a six in his 19-ball stay to give some respect to the Knights batting card.
Medium-pacer Emrit also got Scott Kuggeleijn (4) on the final delivery of the innings to just give away 7 runs in the final over.
With Kings XI Punjab and Hobart Hurricanes already booking a semi-final spot for themselves from this group, a winless Tridents and Knights battle it out for pride in the final league game of the tournament.