Greg Nicol scored twice in two minutes as South Africa beat Argentina 2-1 in the men's Group B hockey match at the Olympics in Athens on Sunday.
Mario Almada had put the South Americans ahead in the tenth minute, scoring with a reverse hit from the top of the circle.
Argentina held on to the lead till the breather but were stunned by Nicol's first goal four minutes after the interval. It upset their rhythm and before they could recover from the setback Nicol scored his second goal, deflecting home a pass from the left which turned out to be the match-winner.
Argentina, the Pan-American champions, launched a last-ditch attempt to share points but were kept at bay by the spirited South African defence in the last 15 minutes.
South Africa, who finished 10th in the Atlanta Games in 1996, were withdrawn from the Sydney Olympics by their home association after the government demanded that more coloured players be included in the side.
They earned a place at Athens only because the International Hockey Federation refused to grant hosts Greece a direct entry to their own Games.
India, defending champions the Netherlands, Australia and New Zealand are the other teams in Group B. The top two team in each group qualify for the semi-finals.
South Africa play India next on Tuesday, while Argentina clash with Australia the same day.