Ben Stokes' Headingley heroics give England hope of achieving what would be their record Test run chase, says batting coach Graeme Thorpe.
Chasing 376 to beat South Africa in the opening Test, England ended day three on 121-1 for their second innings, a marked improvement on their 181 all out in the first.
Rory Burns is 77 not out and Joe Denly remains unbeaten on 10, with Stokes and Jonny Bairstow still to bat along with Joe Root and Jos Buttler, who are both struggling with illness.
Stokes inspired England to an improbable one-wicket win over Australia in the third Test against Australia with a magnificent unbeaten 135 and Thorpe feels the camp have belief a similar result is possible at SuperSport Park.
Asked if Stokes' Headingley knock gives England hope, Thorpe told Sky Sports: "It does.
"It doesn't guarantee us a victory and we know we've got a long way to go, but we were pleased with that. If you gave us this position a day ago we would have taken it.
"We have belief. We've got a chance. If we have a good first session, South Africa will look at the scoreboard.
"We have belief that if we play well, we can put them under pressure. It's always nice to see players bounce back and show character."
Bairstow kept wicket for England with the illnesses to regular keeper Buttler and captain Root the latest in a long list of health issues within the squad.
"It hasn't been a straightforward Test match for us with players coming and going with illness," said Thorpe. "Hopefully Jos Buttler and Joe Root will have another night's sleep.
"We didn't bat well enough first innings. We let ourselves down. The pitch seemed to do a bit more on Friday.
"We'll break it down. We know we've got to play well and when we're in a good position, we've got to be more ruthless."