The Delhi side, coached by Australia's World Cup winning captain Ricky Ponting, needed 18 off three overs against the Kolkata Knight Riders to win their Indian Premier League Twenty match but spectacularly fluffed the chase.
Opening batsman Prithvi Shaw, 19, had made the chase of 186 appear easy but his dismissal on 99 in the penultimate over derailed Delhi who ended up tied with Kolkata's score needing the Super Over to decide the winner.
Kolkata fast bowler M. Prasidh Krishna conceded 10 in the Super Over, leaving the marauding Andre Russell, who scored 62 off 28 balls in the team's innings of 185-8, with a relatively simple task.
But Rabada had other plans as he produced immaculate precision with his yorkers to give away just seven and give Delhi their second win in three matches.
"I was sort of sitting around in my shorts... I was sitting upstairs with Shikhar Dhawan and we were having a chat," Rabada told reporters.
"We thought this game is ours but they say cricket's a funny game. I said to Shikhar 'let's go downstairs, let's go support the boys.'
"Then obviously the match was tied. I was just hanging around there waiting to see who was going to bowl. ... Then they said 'it's you!' So I was like 'okay, cool! Better think of something quickly.'"
The 23-year-old quick, who will be South Africa's leading fast bowler in the May 30-July 14 World Cup in England and Wales, was uncluttered in his head despite being clipped for a four on the first delivery by Russell.
He conceded only three more runs in the rest of the over while also disturbing the stumps of the powerful West Indies all-rounder with his third delivery.
"I thought my yorker was coming out decently this game, so that's what got me to back it even more," Rabada added.
"I think it's important to really be clear and you need to be sure of what you're doing, whatever ball you bowl.
"That was my plan and that's all I tried to do. On a different day, it could be totally something else, on a different day you could be positive with two things that you try and do.
"But today was just the one and that was yorkers. I'm really glad that it came off."
(Reporting by Sudipto Ganguly; editing by Greg Stutchbury)
