Sri Lanka's prolific spinner Muttiah Muralitharan said the Proteas will be tough to beat in the two-match series despite being crippled by the absence of three key players, including captain Graeme Smith.
Smith and leading all-rounder Jacques Kallis are recovering at home from injuries while veteran Shaun Pollock opted to skip the first Test at the Sinhalese sports club following the birth of his second child.
"Lots of people think the series will be a cakewalk for us, but that is not going to happen," said Muralitharan, whose 635 Test wickets are bettered only by Australian record-holder Shane Warne's 685.
"They are a very competitive side. They may lack two or three key players, but they'll still push us hard. We can't take them lightly.
"We may be the favourites because we are playing at home, but we will have to play very well. England is over. You just can't keep admiring past performances," the 34-year-old said.
Sri Lanka enjoyed a successful tour of England recently where they fought back to draw the Test series 1-1 and blanked the hosts 5-0 in the one-dayers.
Captain Mahela Jayawardena hinted that Sanath Jayasuriya, Sri Lanka's most successful Test batsman with 6,621 runs in 103 matches, may once again open the innings, displacing young Michael Vandort who opened in England.
"We have not finalised anything yet but Sanath is a genuine opener and has been successful," said Jayawardena, who also led in England in the absence of regular captain Marvan Atapattu.
"You have got to take tough decisions. Michael has done well, but you can't ignore Sanath for his experience and form."
South Africa's stand-in captain Ashwell Prince, 29, the first black cricketer to lead his country, said the tourists were geared for the battle ahead.
"We will obviously miss our three big players but it's an opportunity for others to show their worth," said the left-handed batsman who has played in 21 Tests.
"We have had a good outing in the three-day game with most of our batsmen getting runs and the bowlers also had a good work out."
Jacques Rudolph, a late replacement for Smith, hit 157 and 58 in the tour opener against Sri Lanka's 'A' team, Hashim Amla made 150 and Prince and A.B. De Villiers scored half-centuries.
Herschelle Gibbs returns as opener to partner Boeta Dippenaar after being dropped from the home series against New Zealand in April-May due to poor form.
Paceman Makhaya Ntini, ranked second behind Muralitharan in the International Cricket Council's Test ratings, spearheads the bowling attack that includes Andre Nel, Andrew Hall and spinner Nicky Boje.
Pollock, who arrives on Thursday, will play in the second Test at the Sara stadium here from August 4.
South Africa: Ashwell Prince (capt), Herschelle Gibbs, Boeta Dippenaar, Hashim Amla, Jacques Rudolph, A.B. De Villiers, Mark Boucher, Andrew Hall, Nicky Boje, Makhaya Ntini, Andre Nel, Dale Steyn.
Sri Lanka: Mahela Jayawardena (capt), Upul Tharanga, Sanath Jayasuriya, Kumar Sangakkara, Tillekeratne Dilshan, Chamara Kapugedera, Farveez Maharoof, Chaminda Vaas, Lasith Malinga, Dilhara Fernando, Muttiah Muralitharan, Malinga Bandara, Michael Vandort.