Stormers head coach Allister Coetzee said on Wednesday that Steenkamp, returning from a chest injury, was experienced in that role, and he had already proved himself, both at Super Rugby and Currie Cup level.
"We've moved Eben back to the number four slot because De Kock is back from injury," said Coetzee.
"I think it is fair to say that we'll have Eben there (on a regular basis) once he's had a chance to get used to the number five role.
"Eben did a marvellous job last week, but given De Kock's past experience in making line-out calls, we've taken that option."
Etzebeth did not train on Wednesday after he arrived at the practice session suffering from a cold.
"We sent Eben home as he had a light cold and that's the way to manage him," said Coetzee.
"Jean (De Villliers) also did not train again. It's a way of managing him."
Steenkamp's inclusion means that Gerbrandt Grobler has dropped down to the bench.
Flank Don Armand is the other forward to be relegated to the bench as he makes way for the returning Deon Fourie, who has been handed the number seven jersey after recovering from a rib injury. Fourie has mostly been used at number six but Coetzee felt he needed to keep Siya Kolisi there.
"We want to keep things simple and that's why Deon's at number seven," said Coetzee.
"Deon's experience will allow him to cope better with the responsibilities."
The weather forecast predicted heavy showers in Cape Town on Saturday, and Coetzee believed the conditions would restrict his team's attacking intentions.
"We know that conditions will be difficult and it won't be conducive to attractive rugby," he said.
"Rainy weather always proves to be a great leveller. Under difficult conditions, it always comes down to quality set-pieces and a good kicking game."
Teams:
Stormers:
15
Joe Pietersen, 14 Gio Aplon, 13 Jean de Villiers (captain), 12 Damian
de Allende, 11 Bryan Habana, 10 Elton Jantjies, 9 Louis Schreuder, 8
Nizaam Carr, 7 Deon Fourie, 6 Siya Kolisi, 5 De Kock Steenkamp, 4 Eben
Etzebeth, 3 Brok Harris, 2 Tiaan Liebenberg, 1 Steven Kitshoff.
Substitutes:
16 Martin Bezuidenhout, 17 Chris Heiberg, 18 Gerbrandt Grobler, 19 Don
Armand, 20 Dewaldt Duvenage, 21 Gary van Aswegen, 22 Gerhard van den
Heever.
Kings:
TBA