Quick hits: Sore Smith doesn't return as Marnus throws it away on horror day

Steve Smith doesn't return after reaching a major milestone and Marnus Labuschagne makes a mockery of an enormous reprieve as Australia is sent barrelling towards a chastening defeat in Gqeberha.

Here are the quick hits from day four of the second Test between Australia and South Africa.

1. Fiery Marco tears through the Aussies

Fresh from his swashbuckling 85 on day three, the towering Marco Jansen continued to terrorise the Australians on day four.

The left-arm seamer was at his fiery, probing best, with his aggression and accuracy proving all too much for the tourists in their first innings.

Jansen dismissed both Scott Boland and Travis Head early in the day, before a few tense exchanges with Marnus Labuschagne appeared to light a fuse somewhere deep in the big man.

He proceeded to treat Matt Renshaw to a send-off — seemingly in Afrikaans — upon having the Yorkshire-born Queenslander caught at short leg, before sending Alex Carey packing in a double breakthrough in the shadows of lunch.

Unfortunately for the Aussies, Jansen wasn't done there, with the South African having Beau Webster caught in the cordon to claim his fifth wicket and continue Australia's horror day.

2. Sore Smith reaches 11,000 and doesn't return

Amid the carnage up the other end, Steve Smith was just about hanging in there.

Struggling with a neck issue, the Australian received running repairs at multiple points during his innings and never quite looked his usual self.

Even so, Smith was at the crease long enough to become just the 12th batter to score 11,000 Test match runs, joining Ricky Ponting and Allan Border as the only Australians in that rare air.

But the Australia vice-captain was in serious discomfort throughout his innings, and departed promptly after joining that exclusive club.

The stiff-necked Smith was bowled through the gate by Wiaan Mulder for 28 as Australia was asked to follow on after being skittled for just 99, their fourth-lowest Test total against the Proteas.

And in a massive blow for his team, the Australia vice-captain did not recover in time to return to the crease as wickets started falling in the tourists' second dig, remaining in training gear in the dugout as Australia limped towards stumps.

3. Two remarkable grabs, two very different reactions

We have been treated to some seriously sensational slip catching in Gqeberha.

Following in the footsteps of Renshaw — who made a stunning low catch late on day two — Simon Harmer produced his own moment of magic early on day four.

With Australia 3-45 in its first innings and already beginning to teeter, the desperately out-of-touch Labuschagne drove unconvincingly, sending his thick edge flying low and hard towards the cordon.

Harmer dived dramatically to his left, using his sizeable left hand to pluck the quickly dropping ball from the air in front of second slip.

And the off-spinner was absolutely pumped with his effort, throwing his head back and roaring as he got to his feet. 

It provided quite some contrast to Renshaw's bewilderment after pouching his similarly excellent catch earlier in the Test.

4. Marnus throws it away after enormous reprieve

With Australia beginning its second innings needing 326 runs to just make South Africa bat again, Labuschagne had a golden opportunity to revive his sputtering Test career and make up for his rash dismissal earlier in the day.

Coming in after the early departure of Nic Maddinson, the signs were good for the Queenslander, who knuckled down with Head to push Australia towards 100.

And it was beginning to feel like Labuschagne might have finally been on for a score when he was the beneficiary of a huge reprieve in the 28th over.

Given out LBW to a Harmer off break, Labuschagne reviewed the decision in a blink and it was high drama as both camps waited for ball tracking to take an unusually long time to build.

Eventually, the technology projected the ball to be missing leg stump by what surely wasn't much more than a coat of paint.

Helmet off and head back, Labuschagne was making no secret of his relief.

But only moments later, he threw it all away, mistiming his slog and holing out to long-on for 39.

It was an ugly, ugly dismissal and one that left Australia once again on the rack with shadows lengthening in St George's.

5. Consecutive night shifts for Boland

With Australia proceeding to lose both Renshaw and Webster late on, Boland once again found himself batting in the dying embers of a day.

It was the second consecutive evening the Victorian had been called on as nightwatchman, and for the second consecutive evening, he made his way through to stumps.

Again, he betrayed no hint of annoyance with his sacrificial role, instead digging in and bravely finding his way through a couple of overs of twilight finger spin.

It was another committed shift from Boland — but boy, it's some reward for taking a five-wicket haul on his return to the team.

He'll begin day five alongside Head (87*) with Australia 4-156 and still 170 runs away from making South Africa bat again.