Pakistan all-rounder Shadab Khan insisted Thursday that his under-performing teammates believe "miracles can happen" as the former champions enter a "do-or-die" battle to rescue their faltering World Cup campaign.

After starting brightly with wins over the Netherlands and Sri Lanka, the 1992 champions have been well beaten by India and Australia before being humiliated by neighbours Afghanistan last time out.

On Friday, they face another test of their resources against free-scoring South Africa who have four wins in five games and have shrugged off their shock loss to the Netherlands.

"We have under-performed in all three departments -- batting, bowling and fielding," said Shadab.

"We have not played good cricket but have bounced back from such situations."

With four group games to play, Pakistan can still make the semi-finals but there is little margin for error.

However, as well as victory on Friday, they also need to improve their -0.40 net run-rate which could prove to be the tie-breaker in the race for semi-final spots.

"If you have belief, miracles happen," said Shadab, the deputy to skipper Babar Azam.

"We have not played like we were playing before the World Cup but from tomorrow we have to start a winning streak."

He added: "When you are in a do-or-die position then I think the pressure is less because you have nothing to lose."

Shadab has been one of many in the Pakistan squad who has yet to fully fire.

The 25-year-old leg-spinner has just two wickets at 90.00 and scored 74 runs in three outings.

He was dropped for the match with Australia before being recalled to face Afghanistan.

"When you don't do well the criticism is valid but there are ups and downs in a player's performance so I am confident that I will improve," said Shadab who scored 40 in the losing cause against Afghanistan.

Shadab insists the shock eight-wicket defeat to Afghanistan in a game also played at Chennai is now behind them.

Victory, he insists, will hopefully quieten the criticism which has grown steadily since the eighth loss in eight World Cup meetings to India.

"I always tell the players that if you are going to a tournament like this, you have to cut off from the social media," said Shadab.

"If you perform then everyone says that 'he is doing so well', but when you are not performing then the same people will say 'he is not good enough'."

He added: "It's the mentality that when someone is not in the team, then they are the best and when someone is in the team they are the worst."

Meanwhile, fast bowler Hasan Ali has become the latest Pakistan player to fall ill and will miss Friday's game.

"Hasan is unavailable for the game against South Africa," said a Pakistan Cricket Board statement.

"He is recovering well and will be given rest to recover ahead of the remaining games.