On Thursday night, either the world champions or the pre-tournament favourites will be heading home.
Had they lost, India would have played Sri Lanka instead, but Yuvraj Singh, man of the match after another superb all-round display (113 and two for 18) insisted that it made no difference who the co-hosts were up against.
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"These are the moments you live for as a cricketer," he said. "To win, we need to beat the best sides."
Yuvraj's place in the side was questioned in the lead-up to the tournament, but it was his 122-run partnership with Virat Kohli that set this game up for India in the absence of Virender Sehwag - missing with knee trouble - and after the early loss of Sachin Tendulkar.
He was reprieved twice, on nine and 13, both times by Darren Sammy, and he admitted that a first century in two years had come as a relief.
"I was nervous. At No 5, you don't get to hit many balls," he said. "So today was an opportunity [at No 4]. It's been a while."
Despite suffering from stomach cramps, Yuvraj played some gorgeous strokes, through the off side and over midwicket, as India recovered from early blows dealt by Ravi Rampaul, playing only because Kemar Roach was down with fever.
Rampaul bowled at 140kmph for the most part and got both Tendulkar and Gautam Gambhir with deliveries that bounced appreciably.
Steve Davis, the umpire, initially gave Tendulkar not out, but Rampaul was soon running towards point in celebration as the batsman turned on his heel and walked to the pavilion.
Sammy accepted that Rampaul's performance was one of the few things to take away from yet another defeat. "He has been on the bench, but he's come in and grabbed his opportunity with both hands. That's what you want from your team set-up."
Rampaul aside, this was another story of missed opportunities. At 154 for two after 30 overs, the West Indies were cruising. Then Zaheer Khan slipped a slower ball past Devon Smith's defence. Before you knew it, they had lost eight for 34 and the game with it. Having lost four for three from a winning position against England, this was another chastening experience for a side that has not beaten top opposition since June 2009.
"It's a good thing it didn't happen in the knockout stage," said Sammy. "If it had, we would be going home. It is worrying for us, but I back the calibre of players that we have."
Smith top-scored with a fine 81, but there was no Chris Gayle alongside him at the top of the order. The West Indies, however, are confident that he will have recovered from his abdominal strain in time for Wednesday's quarter-final against Pakistan.
"Their captain has been performing, and some of the others too," Sammy said when asked about Pakistan. "Hopefully, they'll have their bad match against us, and we'll bring our A game."
India gave a World Cup debut to R Ashwin, and he repaid the faith with a fine spell of two for 41. A carrom ball got rid of Kirk Edwards, and he bowled eight overs in succession through the first two power plays.
The game-breaker, though, was Zaheer, whose mastery with the old ball evokes memories of Wasim Akram.
"Zak took that wicket, and then Bhajji [Harbhajan Singh] got Pollard, and the game changed," Yuvraj said. "On these type of pitches, you just have to keep believing, in yourself and your team."
India last beat Australia in a World Cup game in 1987, but Yuvraj was confident that he and his teammates could change that dismal statistic.
"They've won three World Cups, but the likes of [Glenn] McGrath, [Shane] Warne, [Adam] Gilchrist and [Matthew] Hayden are no longer there.
"[Ricky] Ponting's not in great form. If we get into their middle order, I think we can win."