Duminy first smashed 54 off 41 balls as Daredevils scored a decent 167 for four and then chipped in with four wickets as visitors kept their nerves in the crucial stages of the nail-biting contest to restrict Sunrisers to 163 for eight and record their second successive win at the ACA-VDCA Stadium here.
Needing just 10 runs off the last over with Ashish Reddy and Karn Sharma at the crease, Nathan Coulter-Nile got the former run-out in the second ball of the over.
Mayank's superb save made all the difference in the end and last ball of the match resulted in Sharma getting out, handing Delhi their second consecutive win.
Earlier, Delhi Daredevils managed to get on board a competitive score, thanks to fearless batting by young Shreyas Iyer (60 off 40 balls) and Duminy (54) after electing to bat on a difficult pitch at the ACA-VDCA Stadium here.
Coulter-Nile, Angelo Mathews and Imran Tahir took wicket apiece. Duminy accounted for the top order, seeing off dangerous David Warner (28), Shikhar Dhawan (18), top scorer Ravi Bopara (41) and Eoin Morgan (1).
The Sunrisers got off to a good start with Warner and Dhawan putting on 50 runs for the opening wicket before Bopara coupled with KL Rahul (24) and Naman Ojha (12) to keep Hyderabad always within achieving the total.