The Queensland Reds have burst the NSW Waratahs' bubble in a wet and wild Super Rugby Pacific derby in Sydney.

The Reds overcame all odds to pull off a thrilling and at-times comical 20-16 victory at Leichhardt Oval that must have infuriated Waratahs fans.

With no Taniela Tupou, no Tate McDermott for the entire second half and virtually no ball all game, the Reds still escaped with the four competition points after the Waratahs threw the match away.

Despite torrential rain, the ball handling was surprisingly good from both sides but the Waratahs' kicking game and decision making was atrocious.

Winless wooden spooners last year, the Waratahs surely would have upset the 2021 Super Rugby AU champions if only they'd held their nerve in the final 15 minutes after Ben Donaldson's drop goal put the hosts in front.

Alas, they couldn't.

Ryan Smith secured victory for the Reds with a controversial try 11 minutes from time, after replays appeared to show the replacement lock losing control of the ball before grounding it.

Queensland's win ended NSW's bright start under Darren Coleman - after the Waratahs completed an unbeaten trial run then smashed Fijian Drua 40-10 in last week's competition opener.

The gritty victory came after the Reds lost Wallabies prop Tupou minutes before kick-off due to back spasms in the warm-up, then halfback and captain McDermott limped off in the shadows of halftime.

Apart from a second-minute penalty to James O'Connor, NSW enjoyed all the early running.

But despite dominating first-half possession to the tune of five to one, the Waratahs were unable to convert their pressure into points.

Two hooked penalty goal attempts from Donaldson and a contentious no-try ruling against powerhouse centre Izaia Perese after some dazzling lead-up left the Tahs exasperatingly empty-handed.

When Jordan Petaia soared high to reel in a beautiful cross-field kick from O'Connor to nab the opening try, the Waratahs suddenly found themselves 10-0 down after 20 minutes.

Jake Gordon's captain's call to spurn the chance for a gift three points in front paid off for the Waratahs when No.8 Will Harris broke from the back of a scrum and charged over.

Donaldson's conversion plus a 38th-minute penalty allowed the 'Tahs to enter the sheds for the half-time break feeling much more comfortable, if not quite satisfied, with the score locked up at 10-all.

After a brain-snap chip and chase in his own quarter from the second-half kick-off, O'Connor nudged the Reds back in front with a mighty 45-metre penalty goal.

It was still the Waratahs, though, doing all the threatening.

They went within a whisker of posting an early nomination for try of the year after some dazzling lead-up work from Alex Newsome, side-stepping Dylan Pietsch and Donaldson only for winger James Turner to be denied in the left corner.

A melee ensued with the pushing and shoving almost spilling over in the stands before Donaldson tied the game up again with a long-range penalty of his own.

The No.10's drop goal appeared to have given the Waratahs the win until Smith's late intervention.