Kevin Pietersen said England were intent on completing a 5-0 series whitewash after thrashing South Africa in the third one-dayer at The Oval.
Andrew Flintoff hit an unbeaten 78 and Samit Patel took 5-41 as England eased to a 126-run win for a 3-0 series lead.
"We've come in as underdogs and have hit our straps in every single department," said captain Pietersen.
"The blokes have done an amazing job but we want to improve and want to try to win the series 5-0 if we can."
England are now chasing only the second one-day series cleansweep in their history after they triumphed over Zimbabwe by the same margin in 2001-02.
Pietersen said: "We need to carry on and keep going. The 5-0 thing puts a lot more extra pressure on us as it would take us up to second in the world rankings.
"That is the kind of pressure we want - pressure is a privilege and if we win 5-0 it takes us right up to the top."
Pietersen picked out the fielding and the performance of the three fast bowlers Stuart Broad, James Anderson and Flintoff following the emphatic triumph at The Oval, which came after a 10-wicket win on Tuesday and a 20-run success last week.
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"And the fielding over the last couple of weeks has been second to none."
Flintoff has had a brilliant series, with seven wickets and two scores of 78.
After struggling with the bat earlier in the season, he said some work with former Worcestershire captain Phil Neale, also England's tour manager, had done the trick.
"There's such a fine line between scoring runs and not doing," said Flintoff, who battled on bravely after being hit by a nasty bouncer during his innings.
"But I've worked with Phil, watching the ball onto the bat, and it's nice when you score a few.
"It's more about timing and stroking the ball and stats suggest I score better [batting] at five, getting in when the seamers are still on and accelerating at the death.
"I don't think I've bowled particularly well but Jimmy [Anderson] and Stuart [Broad] bowled very well today."
Left-arm spinner Patel, who also struck a useful 31 in England's commanding 296-7, capped a memorable fourth one-day international by finishing with career-best figures as South Africa's batting collapsed.
And Pietersen praised his former Nottinghamshire team-mate's contribution.
"Samit batted superbly with Freddie. He took a great catch to get (Jacques) Kallis - a huge, huge wicket for us - and then bowled like Sanath Jayasuriya. Brilliant," he said.
Patel said: "It has always been a dream to play for England. Playing with Kev you've got the freedom to play cricket and enjoy it. As an individual you can't ask for more.
"We're not playing good cricket, but I think England are playing unbelievable cricket""They've welcomed me and the cricket's been taking care of itself really."
South Africa coach Mickey Arthur said his players would be playing for their places in the final two matches after falling way below the standards he expects.
"I think everyone is under serious threat at the moment. We're going to need some big performances from them," he said.
"I thought we bowled very, very poorly. I certainly don't think it was a 300 wicket - not by a long way. Your first few overs set the momentum. We gave them a lot of runs early on."
Kallis, standing in as captain in the absence of the injured Graeme Smith, added: "We're not playing good cricket, but I think England are playing unbelievable cricket and are outplaying us in every department.
"We came here to win the Test cricket, but we pride ourselves on our performances and we don't want people to forget what we've achieved here."
The fourth match takes place at Lord's at 1045 BST on Sunday, with the final game a day-night international at 1430 BST in Cardiff.
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