"We saw the game and we were in awe of the physicality they brought, and France certainly turned up too and it was a great showcase for what rugby is about," Sinfield told journalists at England's new Paris base as they prepared to face the Springboks in the semi-final on Saturday.
"We have the utmost respect for them, they play great rugby they know what they are about. They have changed their game and they have a run threat, a kick threat, an unbelievable set piece and defence, so we know what we are up against."
Sinfield, however, was quick to remind everyone that England will not be running out at the Stade de France as the support act as the defending champions parade their way to the final.
"For us this week it is important to get the balance right between understanding what South Africa do but also some of our strengths," he said. "It would be quite easy to be blown away by how good they are so there will be some individuals we need to prepare for."
In their victory over a fiercely powerful Fiji side, England had the best successful tackle percentage of any of the four quarter-finalists, though he quickly said that 86% would not be enough on Saturday.
"I'd like it to be higher, we need to keep improving if we are going to get near them at the weekend," he said. "But we can meet them. We've had some pretty tough challenges during the tournament and we have a few guys in the squad with experience of playing against them.
"We have been improving throughout the 19 weeks we've been together. In the last couple of weeks we've faced teams (Samoa and Fiji) who want to throw the ball about and we knew there would be spells when they caused us problems.
"And against Fiji, although it got very tense towards those last few minutes, it was another challenge for this group to have a big lead and then have it chopped down and still be able to find a way to win."
Sinfield said that it would be a matter of individual preference whether those who played in the final defeat by the Springboks four years ago would use it as motivation or consider it an irrelevance.
"South Africa have had a lot of continuity with the coaching team and the players but a lot has changed in four years for us," said Sinfield, who joined the set up as assistant coach to Steve Borthwick last December.
"This is 2023 now, we're in Paris. We know what we up against and we're really excited by the test we face this weekend."