Sexton: 'Someone said there was 30,000 fans but there was no way it was 30,000'
Andy Farrell’s men put one foot in the quarter-finals of the tournament by edging a classic Paris encounter 13-8 to register a 16th straight victory.
The world’s top-ranked team have a two-week break before returning to Stade de France to complete their Pool B fixtures against Scotland.
“I think we’ve had some big wins in pool stages before, that’s right up there,” said captain Sexton.
“When you play against the reigning world champions, it’s always going to be incredibly tough and it was.
“They didn’t let us down in terms of the physicality of the game but I thought we fronted up and gave some good stuff ourselves in that regard.
“Yeah, it’s right up there but we’ve got to make it count now.
“We’ve got some time off this week with the bye week, then we regroup and we’ve got to back it up against Scotland and make sure we do the business to get out of the pool.”
South Africa remained in contention until the final whistle through Cheslin Kolbe’s score and a Manie Libbok penalty but paid a heavy price for some wayward goal kicking.
Ireland were roared home by an estimated 30,000 Irish fans on an unforgettable evening in the French capital.
Veteran fly-half Sexton felt the “insane” support was a vital factor in securing a statement victory.
“We’ve had some big days before in terms of results in the pools but I’ve never ever seen a crowd like that,” said the 38-year-old.
“Someone said there was 30,000 fans but there was no way it was 30,000.
“It wouldn’t surprise me if there was 60,000 and they were insane throughout. They gave us the lift that we needed.
“Honestly, it’s not lost on us. We talk about it a lot, about inspiring those people that put their hand in their pocket week after week.
“They probably saved for four years to come here and it’s something we refer to all the time and I mean that.
“We play for them and they gave us the edge, fair play to them.”
Springboks skipper Siya Kolisi urged his side not to dwell on the disappointing result as they seek to bounce back in a crucial clash with Tonga.
“The intensity of the game was exactly what we needed for a lot of players that have never played at such intensity,” said the flanker.
“The whole atmosphere was amazing on the field but we know exactly what we need to do as a group.
“We’ve got to lift our heads, we’ve got a big game coming and if we dwell too much on what happened, we will forget to perform next week.
“We need to get through that one and then we can start thinking about afterwards. Tonga is an important game.”