International Quad Series: England lose 48-45 to South Africa in London
Commonwealth Games champions England lost 48-45 to South Africa in their second Quad Series match at London's Copper Box Arena.
The Roses led early on but South Africa dominated the second and third quarters.
England edged ahead again in the fourth period but South Africa, ranked fifth in the world, clung on for victory.
"We've got to sharpen up, we've got to be more clinical," said England head coach Tracey Neville on Sky Sports.
England now need to beat Australia on Sunday, 20 January (18:00 GMT) by five goals or more to win their first Quad Series.
Australia defeated New Zealand earlier on Saturday to remain unbeaten heading into Sunday's repeat of the Commonwealth Games final last April.
"We had opportunities - it's quite disappointing not to push on when we need to take them.
"If we don't take them, South Africa are waiting to swallow them up.
"They (England) just seemed to switch off at times and that is a little disappointing.
"I think the first quarter when we got ahead, the game was not tight enough.
"The style going from New Zealand to South Africa was completely different."
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England were out of sorts in the first half, playing with hesitancy and misplacing a number of passes, while South Africa played with confidence, flair and guile.
Neville's decision to switch captain Serena Guthrie and Jade Clarke's positions for the second half made a difference, as Clarke produced a flurry of interceptions at centre and Guthrie seemed more effective at wing defence.
In an attempt to disrupt South Africa's marauding attacking duo of Maryka Holtzhausen and Lenize Potgieter, Neville brought on Layla Guscoth in place of an ineffective Eboni Usoro-Brown.
The goal defence made an instant impact with a flying intercept as England edged in front in the final quarter.
But they couldn't hang on to the lead as a relentless South Africa - buoyed by a solid centre-court trio of Shadene van der Merwe, Erin Burger and Bongi Msomi - came storming back.
An unforced error from England handed the Proteas the initiative in the closing minutes and they calmly ran the clock down to record a famous win, their first over the Roses since September 2017.
Former England player Tamsin Greenway. speaking on BBC Radio 5 live sports extra, said England will be "so frustrated".
"There are a lot of dejected players, South Africa are so happy with that performance. They got stuck in, they weren't afraid," Greenway said.
"I don't think it's a damaging defeat, it's a world-class team we're looking at."
Australia hold off New Zealand fight-back
Earlier on Saturday, New Zealand were left ruing their slow start that saw Australia open up an eight-goal lead at 14-6.
But the Diamonds couldn't sustain their early intensity and pressure as New Zealand gradually chipped away at the lead.
A resurgent and brilliant Silver Ferns closed the gap to within two in the final period, but Australia held on for a 53-50 win.
England face Australia on Sunday in a rematch of the Commonwealth Games final on the Gold Coast, which the Roses won 52-51.
New Zealand will look to close their series with victory against South Africa at 15:30 on Sunday.
Both matches will be live on BBC Radio 5 live sports extra and you can follow BBC Sport's live text online and via the BBC Sport app.