Cape Town - Former Proteas all-rounder Jacques Kallis admits that South Africa have no further margin for error as they remain winless in the Cricket World Cup.

The Proteas suffered an embarrassing 21-run loss to Bangladesh at The Oval to lose back-to-back games.

The Proteas let themselves down with both bat and ball, as they conceded 330/6 and then replying with 309/8.

"I think you've got to give credit to Bangladesh for the way they performed, it's amazing how far they've come as a team in a very short space of time and the way they batted was particularly impressive," he wrote in his ICC column.

"Hindsight is a wonderful thing, but I understand what Faf du Plessis was doing with the toss and playing the extra pace bowler. However, the wicket just didn't allow it and perhaps he stuck with the tactics a bit too long and should have started bowling a little fuller and straighter.

"Bangladesh got all their partnerships going and once you get over 300 then it always become a tough chase, letting them score 50 or so runs in the final four overs really didn't help either and ultimately proved the difference."

READ: Struggling Proteas can expect harsh words from captain Faf

Kallis expressed his disappointment in the Proteas performance thus far and said that Ottis Gibson and his men need to win every game.

"It's disappointing and frustrating and there is lots of pressure on the next game, otherwise the tournament could be over before it's really started for South Africa," said Kallis.

"The good news is we have another game in just three days, so South Africa can't dwell on this, they will just have move on.

"It doesn't get any easier though against India but it's their first game and our third, so maybe that could give us the edge we need," he said.

"They've not played for a week and maybe they'll be some first game nerves, where as we are settled. Strange things happen in this sport and if we can get a win then I think we can go on a streak and we are still good enough to be a contender.

"There will be no margin for error though. I think you'll need six wins, maybe five with a really good run rate, to finish in the top four, so South Africa almost need to win every game they will play."

"It's great having a game plan but you need to have a back-up when it's not working, I felt we were one step behind the entire match and just tactically a bit off. We need to be a bit smarter," he said.

"Bangladesh took it on and were aggressive and the wicket really suited their bowling too. I was really impressed by Shakib Al Hasan, he's a seriously talented and clever cricketer."

The Proteas have been plauged with injury in the ongoing tournament, with Dale Steyn out of the opening two games, Hashim Amla out after suffering a head injury against Sri Lanka and fast bowler Lungi Ngidi pulling a hamstring strain this weekend after bowling just four overs.

"The injury to Lungi Ngidi certainly didn't help Faf, he's a world-class player and a big part of our attack. You've got to play Dale Steyn against India now, and hopefully he is close to fitness," wrote Kallis.

"We've got to play all our cards and we can't afford anymore silly mistakes at vital stages - these are the best sides in the world and they'll always punish you."

The Proteas take on India at the Rose Bowl on Wednesday at 11:30 SA time.

South Africa's 2019 Cricket World Cup squad:

Faf du Plessis (captain), Hashim Amla, Quinton de Kock, JP Duminy, Aiden Markram, David Miller, Lungi Ngidi, Chris Morris, Andile Phehlukwayo, Dwaine Pretorius, Kagiso Rabada, Tabraiz Shamsi, Dale Steyn, Imran Tahir, Rassie van der Dussen