The Two Oceans Marathon is scheduled for April, followed by Cape Town in May, and the Comrades Marathon in June.
But Gerda Steyn believes it is unrealistic for any elite athlete to attempt all three.
Speaking to SABC Sport, Steyn admitted that while many think she is capable of it, she is not a machine and says the body cannot handle such a load.
The four-time Comrades champion said she is eager to see how the new Cape Town Marathon date reshapes the calendar, but insists she cannot plan around all three major events.
Steyn revealed she would prioritise the Two Oceans and Comrades while skipping Cape Town.
"We've seen in the past that October can be very risky in Cape Town because of the wind."
The two-time Olympian believes the Cape Town shift will benefit some athletes while posing challenges for others.
She added that the change will boost the South African road-running calendar by attracting more international participation.
Steyn, 35, attempted a similar triple last year by running Om Die Dam, Two Oceans, and Comrades before adding the Olympic Marathon in Paris, where she burned out despite being in top shape.
She says that experience taught her the body needs recovery time, and three major races are too much.