Centre Mike Tindall and flanker Richard Hill are also fit to take their place in a full-strength starting XV.
Saracens' Kyran Bracken has also recovered from the back spasm he suffered prior to the win over Georgia and ousts Gloucester's Andy Gomarsall from the bench.
Leicester stalwart Martin Corry comes in as a replacement for Danny Grewcock, the Bath lock forced out with a broken toe.
The other change sees veteran Dorian West replace Mark Regan as the replacement hooker.
Saturday's game is seen by many (non-Samoans) as the Pool C decider, and England need to beat the Boks if they wish to finish top and open up a route to the final in Sydney next month that avoids New Zealand or Australia.
The Pool runner-up would face a probable quarter-final clash with the All Blacks in Melbourne on November 8.
England: 15 Josh Lewsey, 14 Jason Robinson, 13 Will Greenwood, 12 Mike Tindall, 11 Ben Cohen, 10 Jonny Wilkinson, 9 Matt Dawson, 8 Lawrence Dallaglio, 7 Neil Back, 6 Richard Hill, 5 Ben Kay, 4 Martin Johnson (captain), 3 Phil Vickery, 2 Steve Thompson, 1 Trevor Woodman.Replacements: 16 Dorian West, 17 Jason Leonard, 18 Martin Corry, 19 Lewis Moody, 20 Kyran Bracken, 21 Paul Grayson, 22 Dan Luger.
Kick-off: Saturday, 18 October, 20.00 local, 13.00 BST, 12.00 GMT, Live in the UK on ITV1