India will be under pressure to justify their number one ranking by winning away from home when they play second-placed South Africa in a three-match Test series, starting at Centurion on Thursday.

India have not lost a home series since going down 2-1 to Australia in 2004, but their away form has been less impressive and South Africa captain Graeme Smith said they were under pressure to show they could win in foreign conditions.

India have won just one of 12 Tests in South Africa.

'If you are the number one side, then you need to perform consistently around the world, like Australia did when they beat teams in their own backyards. The pressure is on India to show that they can hack it over here," Smith told a news conference on Wednesday.

Overcast and rainy weather should suit South Africa's fast bowlers even more and India's batsmen face a stern trial by pace, bounce, seam and swing on a pitch totally unlike the surfaces they are used to at home.

India are pondering the fitness of left-arm seamer Zaheer Khan, whose absence would be a severe blow in their bid to match a South African attack spearheaded by top-ranked test bowler Dale Steyn.

Zaheer, who has a hamstring strain, would be replaced by uncapped left-armer Jaidev Unadkat or Umesh Yadav, and Dhoni suggested his strike bowler would not be risked with the World Cup only two months away.

"Zaheer is doubtful and we will make a call on the morning of the game," Dhoni said. "He has been our best bowler, he has led our attack in whatever conditions, so it is a blow.

"But we need to see the bigger picture, we have to think about the World Cup too, it is so close and a major injury to one of our best eleven will put us in trouble. If we are not 100% sure he is fit, we will not risk him," Dhoni said.

Smith, who broke his hand in the Test series against Pakistan in the United Arab Emirates last month, will take his place at the top of the South African order.

"I made a much quicker recovery than expected and I'm really excited to come through because this is going to be a big series to be part of," Smith said.

"We've flitted between number one and number two in the rankings over the last couple of years, so this is a really exciting opportunity for us.

"We pride ourselves on performing in these big series, there's a lot of quality on both sides and even on the field, it's exciting to be part of it," Smith added.

Teams (from):

South Africa: Graeme Smith, Alviro Petersen, Hashim Amla, Jacques Kallis, AB de Villiers, Ashwell Prince, Mark Boucher, Ryan McLaren or Lonwabo Tsotsobe, Dale Steyn, Morne Morkel, Paul Harris.

India: Gautam Gambhir, Virender Sehwag, Rahul Dravid, Sachin Tendulkar, Vangipurappu Laxman, Suresh Raina, Mahendra Singh Dhoni, Harbhajan Singh, Zaheer Khan or Jaidev Unadkat, Shanthakumaran Sreesanth, Ishant Sharma.