England captain Jos Buttler left to rue toss decision in huge South Africa defeat
The defending champions won the toss and selected to bowl, but toiled in the heat and humidity and allowed South Africa to amass 399 in their 50 overs.
"It’s incredibly disappointing, we came here with high hopes to play our best cricket and we were short of that and well beaten," England captain Jos Buttler (33) said.
"Potentially we should have batted first with the heat. You always look back on the decisions you made. It was incredibly tough conditions, we saw that with the boys in the field."
England made a good start, removing South African opener Quinton de Kock (30) with the second ball of the innings, but when tall seamer Reece Topley (29) had to leave the field with an injured finger, the game changed.
"Throughout the first innings lots of things didn't go to plan," Buttler said. "We started nicely and then Reece picked up that injury. We then had the unknown of whether he was going to come back (and bowl), so we tried to fiddle a few overs in.
"I thought if we could have restricted them to 340-350, probably on this pitch it would have been a really good chase. They just got away from us at the end."
England slipped to 68 for six in their reply as they tried to force the pace in the face of some disciplined South African bowling.
"We needed to get off to a good start, but the ball did a bit and we had a couple of (unfortunate) dismissals, caught down the leg side and caught at leg slip.
"When those things start happening you feel like the writing is on the wall," Buttler said.
England have now lost three of their opening four games of the tournament ahead of their next game against Sri Lanka on Thursday.
"It leaves us with no room for error, we probably have to win every game from here on in," Buttler said.