London: Faf du Plessis warned his South Africa flops to expect "harsh words" as the skipper fights to save his country's spluttering World Cup challenge.
Du Plessis' side are already in danger of blowing their World Cup bid after two defeats in the first four days of the tournament left their campaign in turmoil.
Thrashed by 104 runs against hosts England on Thursday, South Africa struggled again when they returned to the Oval to face Bangladesh on Sunday.
After Bangladesh posted their highest one-day international score of 330-6, South Africa's attempt to become the first team in World Cup history to successfully chase a total that high fell 21 runs short.
It was a bitter defeat for Du Plessis, who took his share of the blame when he admitted he was wrong to put Bangladesh into bat after winning the toss.
With seven games remaining, South Africa can't afford more slips if they are to make the semi-finals from the 10-team group.
They face title contenders India on Wednesday knowing a victory is essential and Du Plessis promised he would get tough in a bid to spark his side.
"My style of captaincy has always been that there's a line and if you don't perform to that line there will be a lot of harsh words," he said.
"There's a time for strictness, and when you see that a dressing room needs you to be strong and to motivate them. But today was not good enough.
"If guys think they can make excuses for performances like today then they will be challenged - that's a fact. All I can say is that we'll keep fighting.
"I'm extremely disappointed, and gutted to say that all formats of our game at the moment are just not firing.
"To blame bad luck is not just an option for me. You still have to find a way to put in performances and we're just off in some areas."
Adding to South Africa's woes, Lungi Ngidi sustained a hamstring strain against Bangladesh that will rule him out for up to 10 days.
Du Plessis hopes to have key batsman Hashim Amla fit to face India in Southampton after he missed the Bangladesh game following a head injury against England.
However, pace bowler Dale Steyn remains a major doubt with a shoulder injury that has kept him out of the first two matches.