India captain Sourav Ganguly said his team were "outplayed in every department" by reigning champions Australia at Centurion.
In a supposed blockbuster, India's lauded batting line-up was skittled for 125 before the Aussies coasted home by nine wickets.
The thumping defeat leaves India with only a hard-fought win over minnows Holland after two games.
"We were outplayed in every department," said Ganguly.
"We need to pull our socks up. We just didn't put enough runs on the board and should have applied ourselves a lot better.
"That wicket was worth more than 125 runs."
Despite his disappointment, Ganguly refused to be downcast about India's World Cup prospects.
"There's still a lot of cricket left in this tournament," he said.
"We need to win the next four games and carry bonus points into the Super Sixes."
India's one-day form has dipped badly since they beat England in the NatWest Series final in July, a period which included a home defeat to West Indies.
"It's hard to explain why we've fallen off in recent months," said Ganguly.
"It's not that we are not trying, but nothing is falling in place.
"Batting was our strong point, but it is letting the side down."