With Richard Levi striking five sixes up front in a 28-ball 61, the Cobras were set on course for victory, allowing them a stutter in the middle of their chase before they eventually crossed the line with two balls to spare.
What made Parnell’s figures of 4 for 20 all the more impressive was that his victims were the four most prized wickets in the Dolphins line-up.
The left-armer removed Morne van Wyk with his first delivery of the day, and then returned to dismiss Pietersen and Dwayne Bravo off consecutive deliveries just as the former England star was threatening to run riot.
Parnell then had David Miller caught in the deep for 35 towards the back end of the innings, to leave Ryan McLaren (26 not out) to scratch around with the tail for the remaining overs.
The Dolphins did not help themselves in the field as they dropped three catches - most tellingly when Levi was put down off the bowling of Craig Alexander in the first over.
Levi went on to blaze his way to a sublime half-century, and such was his dominance of the opening stand that when he departed with the Cobras score on 64 in the sixth over, Andrew Puttick was only on two.
With the required run rate down to a run a ball, Puttick was able to anchor the innings, scoring 33, and there were no signs of panic when Khaya Zondo (2 for 22) removed Omphile Ramela and Justin Ontong fairly cheaply.
Sybrand Engelbrecht (21 not out) and Lesiba Ngoepe finished the job coolly, giving the Cobras their third win from five games to keep their title defence on track.
Michael Owen Smith