SOUTH African keeper Arendse made some tremendous saves, but two crucial errors as Spain took a 2-1 half-time lead.
Spain, who have already qualified from Group B, took a sensational early lead against South Africa, when Raul pounced on a Barthez-like fumble by Arendse and walked the ball home.
But South Africa showed their resilience, coming back to equalise through Benny McCarthy before half-time.
However, a freekick from Mendieta went straight past the defensive wall into the net with Ardense failing to make a move to stop it to make the score 2-1 to Spain.
If Spain win to top the group they play the Republic of Ireland in the second round on Sunday lunchtime.
In the other game, Paraguay, who have a slim chance of qualifying if South Africa lose, are down to 10-men after Carlos Paredes was dismissed in the 22nd minute for aecond bookable offence.
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