Mitchell Starc has delivered an inspired late spell to leave the Third Test against South Africa delicately poised at the end of a see-sawing day one in Cape Town.

After winning the toss and electing to bowl first, the Australians found themselves staring at a massive first innings total as the Proteas' openers Marques Ackerman and Aiden Markram put on 158 runs for the first wicket - but neither man would reach triple figures.

In fact, four South Africa batters registered half-centuries but none was able to ram home the advantage as a big first innings total went begging as Starc rediscovered his mojo in the afternoon sessions.

It was quite a turnaround for the lethal left-armer.

After going for 0-62 from his first 12 overs of the match, Starc was a different proposition entirely with the second new ball, ripping through the South African lower order with six wickets for just 10 runs from his final 4.3 overs.

South Africa collapsed to lose 5 for 29 either side of tea as the match turned on its head and Australian captain Pat Cummins no doubt breathed a massive sigh of relief.

Starc took the final four South African wickets for just 1 run.

Australian will begin its first innings at the start of play on day two with Matthew Renshaw expected to partner Travis Head at the top of the order.