The 24-year-old scored a superb second-half try before South Africa upped their game and went on to win 38-16 in Durban.
Despite the defeat, Cuthbert did see plenty of positives from Wales' first Test performance and he says they need to be more clinical in Nelspruit.
"It's just the fine margins and that's what international rugby is all about," said Cuthbert.
"If you have a look during the game and how many chances we had to score - I think we had more line breaks than them in the first half and we didn't take any.
"They had half of what we had and they took every one."