'Tomorrow the most important day of the summer' - Lee

Brett Lee expects the final day at the WACA to be the most telling of the summer for Australia and South Africa as both aim to land the first blow in the battle of the world's top two sides. At the tail end of a year that has featured some classic fourth-innings chases, South Africa are hoping to bring down the daddy of them all, while Australia require seven wickets to avoid a second consecutive Perth loss.

"Tomorrow is probably the most important day of the summer for both teams," Lee said. "Whoever wins tomorrow, it's going to set the summer up for them. To be 1-0 up going into Melbourne, if that's the way we can be, that's really going to set the platform for us. The team that walks away here with a win will definitely set their sights on winning the series."

South Africa need another 187 to reach their target of 414 and complete what would be the second-highest chase of all time. The key men Graeme Smith and Hashim Amla are gone and much of the pressure will fall on Jacques Kallis, who is 33 not out, and his partner AB de Villiers, along with the debutant JP Duminy, who is the last of the six specialist batsman.

Australia wrested some of the momentum back from South Africa with a pair of late strikes to Lee and Mitchell Johnson, who destroyed South Africa in the first innings with eight victims. It is a match in which wickets have tended to fall in pairs, and Lee said Australia could get well on top with one or two early breakthroughs.

"We're still in with a very good chance," Lee said. "They need 187 more to win, and being three down going on what happened in the first innings with them losing 5 for 7, anything's possible."

Indeed anything is possible, as India proved last week when they chased down what appeared to be an insurmountable 387 against England in Chennai. Virender Sehwag's brutal 83 set them on the path, and in this match Smith's innings will have proved the decisive factor if South Africa achieve their task.

His 108 made a mountain look like a hill, but he was not lifting his gaze too high with a day to play. South Africa know that if they can bat for two more sessions they will almost certainly win the match and with no demons in the WACA pitch, one of their main jobs is to ensure they carry none of their own after past failures against Australia.

"In my own mind things have gone a lot better than I expected," Smith said. "In our own heads it's really feet on the ground. We know that after two sessions tomorrow we'll probably know where we are."

It helps that South Africa have come back from difficult positions in the past six months. At Lord's in July, they conceded a 346-run lead to England in the first innings and then built a hefty score of their own to save the game. At Edgbaston a fortnight later, they faced a fourth-innings chase of 281 to win the series and got there with five wickets in hand, thanks to another Smith century.

"The confidence that you gain from chasing totals like Edgbaston, batting out at Lord's , each player that's played key moments and been a part of that, you can only gain confidence and strength out of those situations," Smith said. "I think that's the growth in the team. Even if we don't get there tomorrow the confidence that we've gained so far out of this Test match has been huge."