After Matt Renshaw (74) and Cameron Green (65) had Australia moving towards South Africa's first-innings 329 on Wednesday, Marco Jansen removed both just before the break.
The newly-crowned top-ranked Test bowler first drew Renshaw into an uppercut and had him caught behind, before taking Green's edge in the next over.
At 2-184 Australia looked in a good position but within four balls from Jansen, their push to win at Newlands and take the series looked a fair bit harder.
Cricket just doesn't appear easy for Labuschagne at the moment.
He has cut a tense figure all week with his Test career on the line, and carried that approach into his brief innings on Wednesday.
After Travis Head chopped onto his own stumps on 41, Labuschagne was tentative to his first few balls from Simon Harmer in the morning session.
He then went back to a ball he should have gone forward to, edging the spinner to slip.
Labuschagne will almost certainly have another chance to bat in this Test, but he appears a dead man walking.
If Australia had more batting depth on the tour or if this was a home series, he could well have been gone already.
Prior to this match, Labuschagne had scored between 30 and 49 in six of his past nine Test innings.
Australia's captain Pat Cummins put it bluntly last week when he declared those "aren't going to win too many matches" following the big second Test loss.
Labuschagne was the No.1-ranked batter in the world after his first 30 Tests, averaging above 60 and having chalked up 10 centuries in 52 innings.
In the 70 innings since, he has scored just one century and averaged 28.82.
The right-hander has now also gone 48 innings since his last century against England in the 2023 Ashes.
The Queenslander was briefly dropped during a three-Test tour of West Indies last year, but Australia have for a long time had faith in him to lead the batting into the future.
Labuschagne had been in line to play in this Test at Newlands, even before Steve Smith's neck injury prompted the late call-up for Josh Inglis.
But he now appears certain to be axed for Australia's next Test against New Zealand, with Kurtis Patterson, Nathan McSweeney and Sam Konstas leading the contenders to replace him.
With Labuschagne out on Wednesday, Renshaw and Green batted with sound control until their back-to-back dismissals just before tea.
Green had one curious moment, when after avoiding the pull and hook shot all innings he pulled Kagiso Rabada for two straight sixes over the legside.
The first easily cleared the rope, but the second only just flew over Marques Ackerman on the boundary after South Africa had moved the fielder there.
Green briefly admonished himself and appeared as if he had regained his control on return from an abdominal injury, before Jansen's double blow prior to tea put the Test back in the balance.
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