The match also saw a promising return from injury for Springbok centre Adi Jacobs, who not only played a full 80 minutes but showed excellent touches throughout.
It was no coincidence that with Jacobs in the centre the young Sharks XV’s four tries all came from the backs, with De Kock’s brace supplemented by an opening score to centre Riaan Swanepoel and a match-swinging effort by wing Mark Richards.
The Sharks XV opened up an early 8-0 lead when flyhalf Guy Cronjé kicked an 11th-minute penalty and Swanepoel crossed the line with less than a quarter of the game gone.
Swanepoel benefited from a good break by fullback De Kock and quick hands by Cronjé and his twin brother, scrumhalf Ross, to canter over near the right-hand post.
Flyhalf Louis Fouche got the Blue Bulls onto the scoreboard with a 23rd-minute penalty, then traded further successful attempts with Guy Cronjé to make it 11-6 to the home side.
The Sharks XV, who enjoyed a surfeit of possession, made their ascendancy count again six minutes from the break when the elusive De Kock crashed over from close range after eighthman Marcell Coetzee had made the hard yards from a five-metre scrum.
Guy Cronjé made no mistake with the conversion but it was Bulls replacement JC Roos who had the final say in the first half when he slotted a drop goal after the hooter to reduce the deficit to nine points.
Fouche made it a six-point ball game in the 49th minute with his third penalty after poor play by the Sharks near their own posts.
The Bulls’ advantage in the lineouts and set scrums began to take telling effect as the match wore on and the Sharks, so dominant for much of the first stanza, suddenly found themselves unable to break out of their own half.
The dam wall eventually broke on the hour when flanker CJ Stander broke through and Fouche converted to give the visitors the lead for the first time.
Their advantage was short-lived however after great interplay between Jacobs, Richards and De Kock saw Sevens Bok Richards dive over in the right-hand corner for his team’s third try with 12 minutes remaining.
But it was De Kock, the standout player of the day along with Jacobs, who put the matter beyond doubt when he chipped ahead and dotted down for his second try with two minutes remaining and give his side a precious bonus point.
Scorers:
Sharks XV 30 – Tries: Riaan Swanepoel, Kobus de Kock (2), Mark Richards. Conversions: Guy Cronjé, Fred Zeilinga. Penalties: G Cronjé (2).
Blue Bulls 19 – Try: CJ Stander. Conversion: Louis Fouche. Penalties: Fouche (3). Drop goal: JC Roos.