Sydney has clouded over and it is raining; raining in a persistent, determined manner as if the Gods were determined to wash away all the gifts that the SCG is believed to offer Indian cricketers. No sun to start with. An entire pitch block under the covers, clouds, uncertainty; a day of umbrellas opened rather than sleeves rolled.

India's World Cup semi-final is under 48 hours away and it is promising to be overcast and gloomy for the better part of those hours. The Thursday weather report promises what the Indians would want - "cloud clearing." The last thing India need going into their semi-final against Australia is a pitch that has spent maximum time under covers.

If there is any ground they would have liked to have played a World Cup semi-final in (of all the towns in all the world outside India), the SCG would be it. But an SCG with the sun shining and the pitch baked.

In its typical guise, the SCG offers to Indian opponents a sense of "threat perception" - a phrase found in behavioural science, used with regard to individuals and organisations. The threat perception around India at the SCG lies in the fact that their batsmen will feast and the ball will turn.

In the run up to a hair-raiser semi-final, this threat perception is so constant and enveloping that the Australians are said to be mumbling under their breath about the fact that there is not a single blade of grass left on the pitch. The ICC has put the ground into their organisational lockdown since January and it is thus inferred, sotto voce, that the home side will be stripped of all advantage.

In number terms, the idea of a rampaging India at the SCG, particularly against Australia, is largely misplaced. The truth is that Sydney works better for India as a Test venue; in ODIs India have lost 12 of their 14 games against Australia at this ground and won only a single game over the last 35 years. That win came in 2008, in the first of three finals in the CB series, in which it was their seamers who took out three of the top four Australian batsmen inside the first six overs.

Yet the threat perception remains: the former England captain Michael Vaughan stirred in a bit more ominous chatter. "If India were going to play Australia in a semi-final in Australia, the wicket that they would have chosen would be the SCG. I think it will take some spin."

He has a point, given the example of the last match played on the same strip that will host the semi-final. It was the low-scoring South Africa-Sri Lanka quarter-final in which Imran Tahir and J P Duminy picked up seven wickets between themselves. Witnesses of that game believe, though, that not a single ball turned. Maybe one or two, when the batsmen blinked.

It is the prospect of turn that has added weight to India's threat and its best chance of knocking the Aussies off their game. The very idea that the pitch has the Australians grumbling should make the Indians giggle. They know that when Australia go to bat, the key to the game lies in the hands of their Indian spinners. On Monday, Anil Kumble told Wisden India the difference between the sides in the semi-final would be "the fact that India have got quality spin resources and Australia don't." That in the middle overs, when spinners are required to choke the runs and grab the wickets, Australia will have to turn to their part-timers.

The Indian spinners, two specialists and two part-time men, have spent the World Cup largely under the radar. In the first two high-wire group matches against Pakistan and South Africa, the batsmen gave the bowlers fat totals to bowl against and in the rest, the seamers were able to step in, bowling in tandem and in sync. There could be no better ground for the Indian spinners to come into their own at this World Cup than Sydney and in fact, no bigger game.

R Ashwin, the leader of the spin attack, was expertly used by Dhoni in the group matches, bowling within the first 15 overs in both the Perth matches - against West Indies and UAE. Ashwin is among the three top wicket-taking spinners in the tournament, with 12 wickets at an average of 24, an economy rate of 4.29 and a strike rate of 33.5. Like Dhoni has abandoned funky bowling changes during the World Cup, Ashwin has abandoned funky bowling, turning up like a conventional offie, attacking the off-stump rather than the batsman's pads, slowing his pace a little, offering loop.

"I've been really impressed with Ashwin in the tournament," Vaughan said. "He's getting that shape through the air, the drift which is very important to his style of bowling."

Vaughan said Ashwin would have noticed Tahir's impact in the Sydney quarterfinal and "thinking I can do that job. It will come down to certain players winning their battles." Ravindra Jadeja has been inconsistent through the tournament, but on a ground where Kumble says the pitch actually quickens as the game goes on, there is always the possibility, most certainly the threat, that it is he who could be the jack in the box.

Yet there is no doubt as to who Australia will most worry about. Ashwin is close to his 100th ODI for India and whatever else his performances overseas have been like, it is in the big, multi-nation events in short form cricket that he has been able to stomp his lumbering presence on the game with 49 wickets at an average of 19. Earlier in the the tournament, Ashwin had talked about the approach to take during big events and on big days. "If you look around within your team or outside your team, you always see a lot of insecurities. I try to capitalise on the insecurities of the other cricketers; as much as I'm insecure, they're also insecure."

Once a cricketer is able to locate their rival's uncertainities, the opponent's threat perception vanishes. Australia must know where India's lie too. Beneath the covers, the pitch continues to sweat. So does everyone else around Thursday's semi-final.