England captain Jos Buttler accepted the champions "have no room for error from here on in" at the World Cup after a record 229-run defeat by South Africa.
The Proteas piled up 399-7 after Buttler sent them into bat in Mumbai on Saturday, with Heinrich Klaasen defying the hot and humid conditions at the Wankhede Stadium to post a gutsy hundred.
England, having conceded their highest one-day international total, then collapsed to 170 as they suffered what was also their record loss at this level.
They have now lost three of their first four games -- a nine-wicket hammering by New Zealand and shock defeat by Afghanistan also on their record -- with another defeat likely to scupper their hopes of qualifying for the semi-finals.
"It certainly leaves us in a tough position," said Buttler, whose side next play Sri Lanka on Thursday.
"There's no room for error from here on in.
"It's going to be incredibly difficult. We haven't left ourselves any margin from this point in. But we'll keep the belief. We'll sit down and go again."
England's bowlers were powerless to resist as Klaasen (109) and Marco Jansen (75 not out) shared a sixth-wicket stand of 151 in just 77 balls.
Faced with an enormous chase, England's batsmen felt compelled to go for their shots against a proven South Africa pace attack.
But there was still something alarming about the way in which they were dismissed in 22 overs.
"I think it's obvious that we're not performing to our best," said Buttler.
"It's my job as captain, along with the rest of the team, to work out how we can get back to playing that brand of cricket, playing to our potential and getting back to our best.
"It certainly won't be anyone giving up or having those kind of thoughts. We'll just have to dust ourselves down and stick our chests out and go again."
Saturday's result might have been different had Buttler opted to bat first after winning the toss.
As it was, his decision to field exposed the whole of England's XI to the energy-sapping conditions, with the temperature soaring to 36 degrees.
"With hindsight, with the physicality of that innings, potentially batting first would have been a better decision," Buttler said.
"It's a decision I took at the time. I thought it was the right one and I still believe if we were chasing 340, 350, we would have done really well in those conditions."