Winger JP Pietersen scored two tries as the Sharks beat the Chiefs 22-15 in the Super 14 on Saturday.Pietersen's tries in the 15th and 28th minutes of the second half ensured the Durban-based Sharks kept their unbeaten record through three rounds, while the Chiefs lost their third straight match by seven or fewer points.The Chiefs were unlucky, crossing the Sharks line three times only to be denied tries on video replay by the television official. On several other occasions they seemed certain to score but were frustrated by poor handling, wayward passing or a saving tackle by a Sharks team that defended courageously.The Chiefs battered the Sharks goal line for almost all of the last 10 minutes of the match, seeking the try which could earn them a draw, but the South Africans’ defence held out until the gripping match ended in the fifth minute of stoppage time."It's bloody gutting when you look up there at the scoreboard," Chiefs assistant coach Craig Stevenson said. "We showed a lot of guts and a lot of pride but we didn't come away with the points tonight. It's very disappointing."But they've got to be proud of the defence they put up in that last five minutes. It was outstanding."Both teams had exactly 50 percent of possession in a game in which almost all other key statistics were even.The Chiefs scored first after 14 minutes through a penalty by flyhalf Stephen Donald but the Sharks took a 7-3 lead to halftime after a 31st-minute try to centre Francois Steyn, converted by Rory Kockott.The Chiefs led again after eight minutes of the second half with an unconverted try to hooker Aled de Malmanche, one of the keys to an outstanding forward performance. The Sharks quickly wrested back the lead with a penalty to Kockott, who landed three goals from four attempts.Springboks winger Pietersen's tries saw the Sharks build a 22-8 lead after 68 minutes. Steyn put in the kick that led to the first try and flyhalf Ruan Pienaar the crosskick which produced the second.The Chiefs seemed beaten and had lost momentum to basic errors but they regrouped and came back immediately with a try to halfback Brendon Leonard with ten minutes to go, converted by his All Blacks teammate Donald.Prop James McGougan, flanker Liam Messam and replacement wing Mike Delaney all crossed the Sharks line during the second half but were denied tries.Lock Kevin O'Neill wasted an opportunity, dropping the ball with the line open after a crosskick from Donald."It was a very disappointing evening," Chiefs captain Messam said. "But the boys showed a lot of heart and a lot of courage so at least we take some positives from that."Scorers:Chiefs Tries: Brendan Leonard, Aled De Malmanche. Conversion: Stephen Donald. Penalty Conversion: Stephen Donald. Sharks Tries: Francois Steyn, JP Pieterson (2). Conversion: Rory Kockott (2). Penalty Conversion: Rory Kockott.