Both players were injured in the second Test victory in Johannesburg and will be assessed in the coming days.
Flanker Alberts, who scored the opening try in the 36-27 win, has a knee problem while full-back Lambie, himself a replacement for the injured Zane Kirchner, has an ankle problem.
Coach Heyneke Meyer said: "They will be treated by our medical team in the next few days and we will decide by Wednesday, when we name the team, whether they will play or not."
Another injured player, lock Juandre Kruger, has had a precautionary X-ray and a scan on his neck but has been given the all-clear.
Meyer will be forced to make at least one other change with inside centre Frans Steyn due to get married on the day of the game.
Steyn has withdrawn from the squad which has now travelled to Port Elizabeth from the capital.
A decision on whether replacements are needed will be made in due course.
South Africa hold an unassailable 2-0 lead in the three-match series.
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