De Kock glad of Caribbean experience as South Africa squeeze past England
The opener's typically dashing 65 was the cornerstone of South Africa's seemingly modest 163-6 after they lost the toss in a daytime game in St. Lucia on Friday.
Fine bowling and fielding then reduced England to 61-4 before a stand of 78 between Harry Brook (53) and Liam Livingstone (33) took the title-holders close.
But Anrich Nortje denied England the 14 runs they needed off the last over as they finished on 156-6 and the Proteas edged closer to the semi-finals after a second win in two Super Eights games.
Afterwards, England captain Jos Buttler said the powerplay had been decisive, with South Africa 63-0 off the first six overs compared to their opponents' 41-1.
"Obviously, it makes a massive impact," said De Kock, 31.
"I've played a lot of day T20s in the West Indies (in the Caribbean Premier League) and generally that is the most important time to score runs," explained the left-hander, whose 38-ball innings featured four fours and four sixes.
"The wicket looks beautiful at night, plays much differently, but 160-170 are winning scores here in the day."
Buttler, reflecting on the match, said: "I'd say it was lost in the powerplay...The way Quinny played at the top really put us under a lot of pressure, he played some great shots and we were unable to do that."
Brook almost turned the game England's way before he fell off the first ball of the last over when South Africa captain Aiden Markram held a superb running catch over his shoulder.
"It was a great catch and that's what South Africa have prided themselves on over a long period of time," said Buttler.
"They've always had great fielders, you think of Jonty Rhodes, Herschelle Gibbs, AB de Villiers. They've always been a great fielding team."
England, however, remain in semi-final contention as they head into their next match against the United States in Barbados on Sunday.
"We're still in it and we're looking ahead to the next one," said Buttler.
South Africa take on the West Indies in their final Super Eights game in Antigua on the same day.