Lancaster conceded England have a shortage of scavenging flankers like Australia's Michael Hooper, who got the better of Robshaw at Twickenham and was named man of the match.
Robshaw topped the turnover charts on England's summer tour of South Africa but he will face a different challenge on Saturday, with Francois Louw another nose-to-the-ground flanker.
Lancaster dismissed the idea of Robshaw being switched to the blindside, with Tom Wood likely to replace Tom Johnson in the six jersey.
"Chris has been named captain for the series and I'm more than happy with his contribution on and off the field. I don't see that Chris' performance would warrant being dropped," Lancaster said.
"There are not many in my opinion who play at seven in England in the same way as Michael Hooper or Richie McCaw do. It's quite hard to magic someone up to play in that way in our competition.
"There's a natural instinct players have to become sevens. I know because it's the position I used to play, though I was not quite big enough or tough enough for the highest level."
Worcester's Matt Kvesic is on Lancaster's radar along with Andy Saull, although his progress has been hampered by a lack of game-time for Saracens.
And then there is Steffon Armitage, who was honoured on Monday night as the best foreign player in the French Top 14. He fits the bill perfectly but is currently unavailable.
England have a policy of not selecting overseas-based players and Lancaster appears unconvinced that Armitage can cut it at the highest level.
"I want our players to stay in England and play in England," Lancaster said.
"At Toulon he plays behind a dominant pack and they have got world-class players in every position. They are beating everyone on the front foot.
"To play for 80 minutes, at the highest level in Test rugby, when you're not on the front foot and have to keep running around at high levels of intensity, you've got to be fit."
Robshaw's decision-making was also in the spotlight after he turned down penalty shots at goal and England failed to score a try.
England held a review session on Monday, in which the key decisions not to kick penalties for goal were analysed and the focus shifted to the Springboks.
"I won't criticise the players for having a mindset to win the game," Lancaster said.
"But we have to make sure we get those decisions correct. Did we get them all right? There are some that have been reviewed.
"We can't feel sorry for ourselves. We have to roll out sleeves up and get stuck into South Africa."
Lancaster confirmed he will make changes, with Wood set to come in for Johnson while Alex Corbisiero is primed to replace the injured Joe Marler at loosehead prop.