Australian batsman Mike Hussey believes Saturday's play will be decisive in determining the result of the second Test against South Africa at Adelaide Oval.
Although Australia began day two in a commanding position at 5-482, they lost 5-56 in quick succession and had to settle for 550.
The Proteas came into bat on the stroke of lunch and despite a defensive performance, managed to finish Friday at 2-217 and cut Australia's lead to 333 runs, following a valiant unbeaten century to captain Graeme Smith (111 not out).
Given the sweltering and dry conditions expected in Adelaide on Saturday, Hussey felt both sides' resolve would be tested in an attempt to gain an advantage.
The veteran left-hander was adamant the five-day encounter would produce a result and said Australia needed to regain momentum on Saturday to stand a chance of toppling the visiting Proteas.
"In the context of the whole match, tomorrow is a really key day," Hussey said.
"If we can bowl really well and restrict South Africa then I think we are in a great position to really move forward and win this Test match.
"With a hot day in store tomorrow, we might see a bit more turn coming out of the pitch as the day wears on and hopefully maybe some more variable up and down bounce as well.
"If they bat really well and bat throughout the day though and get up really close or level or even passed our score, then it goes back to being a really even Test match again.
"Adelaide Test matches generally do bring results but they generally bring the results on the fifth day, so tomorrow's a pretty big day in the Test."
Although South Africa were incredibly taxing at times in their innings and reluctant to attack Australia's bowlers, Hussey defended the Proteas' approach.
"It's a difficult situation because when the opposition has 550 on the board you can't really afford to come out and play too aggressively because if you do lose wickets then you're going to be well behind," Hussey said.
"I think it was important for them to make sure they stay in the game as long as they can.
"The Adelaide Test match is quite often not won in the first couple of days but it can be lost in the first couple of days so I felt they applied themselves very well.
"They batted extremely well and have got themselves into a position where they are definitely still well and truly in the match."
Australia looked to have turned the match further in their favour when Smith was given out on 78 after appearing to slightly edge a ball behind to wicketkeeper Matthew Wade.
However the Proteas skipper challenged the ruling and was given not out upon review, after neither replays nor 'hotspot' could prove the ball had glanced the bat.
"If I'm speaking honestly, I actually didn't hear anything but most of our boys thought they heard a noise," Hussey said regarding the decision.
"In my opinion had Graeme hit the ball and was given out by the umpire I think he would have walked off.
"That tells me that he obviously didn't hit the ball, and the technology backed that up because there was nothing on hotspot and there sounded like there was nothing on the effects microphones either."