Springboks 'rain' supreme to drown Wallabies' hopes of shock win

South Africa's B team have come up trumps in Perth's big wet, with the world champions scoring four tries to nil to secure a 30-12 win over the Wallabies.

In a Rugby Championship match blighted by periods of driving rain, the Wallabies only trailed 11-9 at halftime in front of 58,197 fans at Optus Stadium on Saturday night.

But the Springboks piled on three tries from rolling mauls in the second half to secure the bonus-point victory.

South Africa achieved the comprehensive win despite making 10 changes to their starting line-up from last week's 33-7 win over the Wallabies in Brisbane.

Heavy rain in Perth throughout Saturday meant smart rugby was needed on the slippery surface, and the Wallabies largely failed the test during the opening 20 minutes.

Noah Lolesio's third-minute penalty got the Wallabies on the board early.

But they gave up field position a minute later when Andrew Kellaway tried to catch a bullet kick, only for it to slip through his fingers and go into touch.

Wallabies winger Marika Koroibete's attempted chip and chase would have led to a South Africa try if not for Sacha Feinberg-Mngomezulu's fumble with the try line in sight.

And Lolesio's audacious cross-field kick in defence that was picked off by Springboks winger Makazole Mapimpi almost proved disastrous, with only a try-saving tackle from Tom Wright keeping South Africa at bay.

A Wallabies fumble in attack led to South Africa's first try in the 17th minute, with the Springboks racing the ball forward before a dribble kick allowed fullback Aphelele Fassi to dive over.

Two Lolesio penalties - including a tough 45m effort from near the touch line - reduced the deficit to 11-9 late in the half.

And the Wallabies would have entered the break with a one-point lead if not for Lolesio missing a straightforward penalty after the siren.

Wallabies skipper Allan Alaalatoa copped an accidental elbow from teammate Len Ikitau on the stroke of halftime, and he was replaced by Zane Nonggorr after the break.

Returning prop Angus Bell was also brought off at halftime in a move that thrust James Slipper into the action.

Slipper's stint lasted just eight minutes before he was ruled out with concussion.

South Africa extended their lead to 18-9 early in the second half when flanker Marco van Staden crashed over from a rolling maul, before Lolesio's fourth penalty closed the margin back to six points.

Hunter Paisami limped off in the 48th minute with a left leg issue, bringing on Max Jorgensen for his Test debut.

It meant Jorgensen and his father Peter became the 14th father-son pairing to feature for the Wallabies.

The Springboks opened up a 23-12 lead in the 63rd minute courtesy of another rolling maul from a line-out, with substitute Malcolm Marx touching down this time.

Any hopes of an Australian victory evaporated in the 73rd minute when Seru Uru was sin-binned and Marx scored his second try from the next play - again from a rolling maul.