An 80th minute Sharks try for a 22-20 victory put a major and probably fatal dent in the Blues' Super 15 playoff prospects.
After an awful first half effort, the Blues bounced back from a 5-17 deficit to lead by 20-17 in the dying moments of the match at Kings Park in Durban.
The South African strugglers - whose coach John Plumtree departed just days before the match - launched a series of drives at the Blues line before spinning the ball wide to Riaan Viljoen who ducked inside Rene Ranger's covering tackle to clinch the victory.
In a scrappy, low-quality game, the Sharks owned the first half and repeatedly smashed the Blues scrum throughout the 80 minutes. But the home side lacked penetration and suffered through a horror goalkicking effort from Patrick Lambie, who landed three from eight attempts.
In contrast, the Blues looked the more dangerous with ball in hand, but didn't give themselves enough opportunities to make enough of that advantage.