Springbok boss Heyneke Meyer admits he is "worried" about the tiredness of his charges as their June Test duty comes to an end against Scotland in Port Elizabeth on Saturday.
Meyer has expressed his concern over the sheer volume of rugby his players are subject to.
"I almost don't want to say it, but I'm worried about the state of the players. I've never seen the players so fatigued or overplayed at this stage of the year. And I'm not saying this to make excuses," admitted Meyer.
The head coach's battle-hardened number eight, Duane Vermeulen, who turned in a typically bruising display in his home town of Nelspruit as the Boks edged Wales on Saturday, admitted the visitors were the better side.
"They were physically up there and definitely the top team on the night," conceded Vermeulen.
"It's good for team moral and spirit [to have had a close battle]. The good fight from every guy in our squad ... you've got to commend the guys that came off the bench and the spark the guys brought.
The Springboks were chasing the game for the majority of the match, with a shock defeat on the cards for the hosts.
Prop Jannie du Plessis said the team dug deep to snatch victory, which the Springbok stalwart said was a testament to the side's temperament.
"For 80 minutes we believed we can and we will win. If you play for the Springboks, it is probably the biggest thing you can ever achieve," claimed du Plessis.
"You want to go out and win every test by 60 points and you want to smash guys, but unfortunately [it] doesn't always work out like that.
"You have to commend the fire that stayed in their [the Springboks'] eyes."
Du Plessis spent the final anxious 20 minutes of the match watching his teammates salvage victory in the dying minutes.
A penalty try awarded to South Africa, after a shoulder charge by Wales full-back Liam Williams on Cornal Hendricks as he was en route to the try-line, ultimately led to the 31-30 victory.
The Springbok prop believed the side could still have pulled through even if the penalty try was not awarded.
"I am a hell of an emotional guy and I was praying out loud next to the field and I get a stomach ache when watching a match from that side," added du Plessis.
"Whether it was a penalty try or not, I knew we would get a penalty or a lineout, so we would have had another chance."
Du Plessis was also impressed with the resolve shown by his teammates to chase victory until the last seconds of the encounter.
"Of course in sport there is an unknown factor called character. You can't coach that, you can't simulate that in training, and you can't be a psychologist to put guys under pressure the way they were [under] today.
"It is a massive, massive victory for our own belief and we know we can win even though the chips are down."