The 25-year-old has missed Wales' tour against the Springboks, but he saw enough in the 31-30 loss on Saturday to take positives.
Wales led 30-17 with eight minutes remaining and seemed on the brink of recording an historic first victory over the Springboks on South African soil, but panic set in following Willie le Roux's converted try.
However with games against South Africa, New Zealand and Australia on the horizon in November, Warburton insists they can build on the performance.
"I thought it was our time but, mind you, we have been in that situation so many times, against Australia more often. I just can't believe it's happened again," Warburton told Wales Online.
"What that game does do is give Wales great hope for the autumn series - there was still plenty of positives."