Birmingham - There are few who would argue with the fact that Quinton de Kock is South Africa's batting trump card. 

The left-hander opener is still just 26-years-old, but with 111 ODIs to his name, he has become one of the senior members of the Proteas squad in all formats and is a central leadership figure in the team. 

Not known for being overly wordy in front of the camera, De Kock's cricketing mind has always been respected by those around him and it saw him captain the Proteas for T20 ODIs in Sri Lanka last year. 

An ODI average of 45.60 at a strike-rate of 95.39 clearly illustrates De Kock's destructive powers, but his importance at this World Cup has been exemplified by South Africa's top order struggles. 

During what has been a nightmarish campaign so far, the Proteas top order batsmen have not been able to turn their starts into match-winning innings. 

De Kock, with a pair of 68s against England and Afghanistan, is guilty of that too but he is the Proteas' leading run scorer at the tournament with 186 from 5 knocks including the washed-out match against the West Indies when he was 17* before the rain came. 

He has already accumulated more runs at the half-way stage of the 2019 edition than he did throughout the entire 2015 World Cup. 

De Kock was disappointing throughout that campaign, amassing just 145 runs in 8 innings at an average of 20.71.

That seems like an age ago now. 

"In 2015 I was young ... well, I'm still a youngster now ... but back then I was really a baby," De Kock told media at Edgbaston on Tuesday ahead of Wednesday's tournament-defining clash against New Zealand. 

"I was playing my first ever World Cup. I think I put too much pressure on myself. I really wanted to do well.

"And now that I see it a second time, I understand what I did wrong in the first one, and I understand what needs to get done now.

"It's just being mentally free and just trying to enjoy my cricket as much as I can, not like last time in the World Cup. There were too many pressures on myself, or I was putting too much pressure on myself.

"This year I'm trying to take it as easy as I can and just try and do my best."

There is no doubt that a free-spirited, clear-minded De Kock is good news for the Proteas. 

South Africa go into the clash against New Zealand as underdogs and with their tournament one defeat away from almost certain failure and they will need their biggest players to stand up.

Because of De Kock, South Africa will always have a chance against any opposition given his natural ability to tear apart attacks and take the game away. 

The Proteas could do with one of those familiar knocks from their main man on Wednesday, and De Kock believes the side is in good shape to produce a winning performance. 

"We just need to be mentally strong, I think," he said.

"I think that's the only thing that's going to change.

"I think we've been a pretty successful ODI team over the years, so we don't need to change anything.

"It just becomes a mental game at World Cup, trying to deal with all the pressures and stuff."

If the Proteas do win on Wednesday, it will be the first time they have beaten New Zealand in five attempts at a World Cup and their first since 1999, which came at Edgbaston. 

Wednesday's clash gets underway at 11:30 (SA time). 

@LloydBurnard is in England covering the 2019 Cricket World Cup for Sport24 ...