England pace bowler Graham Onions may be ruled out of the opening match of the three-Test series against South Africa starting at the Oval on Thursday after a hamstring strain forced him to miss training on Wednesday.
Onions, who played in the third Test against West Indies this year, is competing for the third fast bowling slot with Tim Bresnan and Steven Finn.
South Africa would overtake England at the top of the world rankings if they win the series and England captain Andrew Strauss told a news conference on Wednesday he expected a lively start to the series.
"South Africa are a very fine side and they'll be determined to knock us off our perch," Strauss said.
"There will be an extra bit of spice because it's the two best teams in the world, but every series I've played against South Africa has always been very keenly contested and I don't think this will be any different.
"I'm certainly very excited about it and it will be a good gauge for us. The rankings say we are number one and we have to go out and prove that now."
England's most recent home series defeat was against South Africa in 2008.
South Africa fast bowlers Dale Steyn and Morne Morkel are accustomed to English pitches as are leg-spinner Imran Tahir and swing bowler Vernon Philander, who both have English county experience.
"South Africa have a very fine bowling attack," added Strauss.
"There are no easy Test attacks to face and we are not approaching it any different.
"We always expect the opposition to be hard to overcome and we'll be going in with that attitude tomorrow."
South Africa captain Graeme Smith, who scored two double centuries in his first Test series in England in 2003, said there was more pressure on England than on his side.
"I guess being chased by a pack does come with pressure," Smith said.
"It's going to be the first major defence of their number one ranking."
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