De Grandhomme and Bruce put on 109 runs for the fourth wicket as the Kiwis chased down their target of 162 with two balls to spare.
X-rays revealed the right-arm paceman had sustained a small fracture to the middle joint while he was fielding a ball at practice on Saturday.
Malinga's impressive returns of 2-23 were not enough to subdue Ross Taylor's sublime 29-ball 48 as New Zealand achieved victory by five wickets.
Taylor lifted New Zealand from a precarious 39 for three in their chase of 175 to complete the win in 19.3 overs and lead the three-match series 1-0.
In hindsight, Guptill has ambivalent feelings about the peculiar final: "I guess you see it as the best and the worst day of your cricketing career.'
In hindsight, Guptill has ambivalent feelings about the peculiar final: "I guess you see it as the best and the worst day of your cricketing career.
Karunaratne clarified to his teammates that he expects his batsmen to use their freedom with prudence.
Sri Lanka were bowled out for 122 runs after New Zealand declared their second innings on 431 for six with a first-innings lead of 185.
De Grandhomme, scoring 83 off 75 balls, and Watling, on 81, put together an unbeaten 113-run stand for the sixth wicket to frustrate Sri Lanka.
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