The relief that Ireland were going to make it to half time with their heads above water quickly made way to fear at the sight of Tadhg Furlong down, holding his ankle.
The tighthead had just contributed to a brilliant defensive set for Ireland, James Ryan's lineout steal flicked back over his own tryline, and it took the brute strength of Furlong to force his way back out and avoid conceding a five metre scrum.
He looked uncomfortable though, and it was no surprise when he failed to return for the second half. But considering South Africa's pack had been in relative control for the first 40 minutes, you'd have backed them to hammer the nail in the second half, with Ireland deprived of their most crucial forward.
The fact that Ireland won without Furlong is as big a boost as the result itself. Better yet, they had the better of the scrum in his absence, with three second half penalties won off the Boks.
Finlay Bealham is no rookie, and Andrew Porter's move across to loosehead has seen him exposed to regular Test rugby, which he now looks comfortable in. Of his 25 Test caps, 12 have been won in the last 18 months, and he's featured in all but two of Ireland's games since the summer of 2021.
On Saturday was on top of Steven Kitshoff at the scrum, and although Ox Nché got the better of him on one drive, the Springboks were lucky to get away with an early shove on that occasion.
Around the pitch, Bealham also helped provide secure ball with 16 ruck arrivals, a solid tally for a 40-minute shift.
"He was awesome," head coach Andy Farrell said of Bealham's contribution.
"Finlay coming on, he has grown in confidence every single time he has come on the field at international level. I thought his scrum was excellent, he was nice and dynamic, nice and low, and never looked like budging. We're delighted for him and he's growing in confidence week by week."
The growth of Ireland's squad depth was also evident in the performances of Stuart McCloskey and Jimmy O'Brien.
Already without the suspended Bundee Aki and injured Robbie Henshaw, it was cruel to see McCloskey's return to Test rugby ended after just 28 minutes due to a shoulder injury, particularly with the Ulster man having been Ireland's best player in the opening half-hour.
A 'next man up' mentality is the mark of a top team, and the way O'Brien seamlessly fitted into the centre is a good reflection on how they are led, both in the playing and coaching group. The debutant didn't produce highlight-reel rugby, but he looked assured and confident in every move he made, even if he admitted to a few nerves afterwards.
His final pass for Mack Hansen's try may have looked simple, but his determination to straighten up his line and suck in the last defender gave his winger the best possible opportunity to score.
His kicked well, his left-foot option used multiple times to exit the 22, while defensively he was resolute, denying Cheslin Kolbe a certain try in the second half, even if Franco Mostert would ultimately score a few phases later.
After the game, Andy Farrell wouldn't take the bait when asked whether he believed Ireland have shown they have the squad depth to win the World Cup, but he will certainly be pleased to have ground out a win against next year's pool opponents while digging deep into his depth chart.
This week's visit of Fiji will also likely provide further opportunities to examine their depth.
McCloskey's shoulder issue doesn't appear to be serious, according to Farrell, and with Robbie Henshaw carrying a hamstring issue, it could allow for O'Brien or James Hume to come in and partner Garry Ringrose in the centre.
Furlong is unlikely to be risked, especially with Australia visiting next week, and that should allow Bealham get a start, with time off the bench for Tom O'Toole, or maybe even Marty Moore, who has been in exceptional form this season.
And with Conor Murray suffering a groin injury on Saturday, Craig Casey will be expected to get a run out.
"The way the game is so attritional, you're going to need 30 or 40 players to be really competing," said captain Johnny Sexton, about the depth of their squad.
"You can't have any weaknesses in your squad and we're building that. The guys that came in today did a great job. It was seamless and that's what you want.
"That comes from great prep during the week, making sure guys are on top of their detail and ready to go. Some guys have to cover multiple positions. Jimmy [O'Brien] could have come on anywhere today and he had to be nailed-on in all of them. Credit to them."
Beyond the squad depth, Saturday's win ticks a very important box for this Irish team, who have often struggled to deal with sides who have had a size advantage.
The 'official pack weights' graphic during the game gave the Springboks just under 60kg of an advantage over Ireland at scrum time, and while those exact figures often have to be taken with a bit of salt, it certainly pointed to a considerable gulf in size and weight.
The gulf could be seen in the individual collisions, particularly in the first half, where the Springboks controlled the gainline, and caused huge disruption at the breakdown, but as a collective Ireland's forwards were better. As mentioned earlier they came out on top in the scrums, while their defensive maul was so tight as to be vacuum-packed.
"Yeah, it builds on our confidence in different areas, doesn't it, because it’s a different type of game than has been thrown at us over the last couple of years. That’s definite," Farrell added.
"But having said that I think the belief was there anyway. The forward pack were excited at what was coming against them and I’ve constantly tried to drill into them that the whole time that this is where you want to be. You want to be tested, you want to find out about yourself, you want to be of a state of mind that’s 'well, it doesn’t get better than this, let’s have a go at it.’ And I’m certain that’s how the forward pack felt this week.
"I think they come out pretty well and I’m sure that their forward pack would think the same as well because the contest was of that nature."
