Australia host South Africa this evening at the Subiaco Oval, Perth, for what could be a decisive match in this years Tri-Nations. Australia, and their coach, Robbie Deans, in particular, are under pressure having lost the the first three games of their campaign. There was slight cause for optimism in their performance last week, especially in defence, but they were unable to hold out against an improving All Blacks' second half offensive.

They have the unenviable task of facing the pace-setting Springboks, although history does indicate they have a chance as the South Africans are not good on their travels and have only won three times in Australia since their readmittance into international rugby. However, they are living up to their billing as world champions and their controlled kicking and power game makes them clear favourites. A win today would effectively, if not mathematically, seal the trophy for them.

Join me, Jamie Allaway, at 18.05 local time (10.05 GMT) for full commentary on this crucial game.

11:00 The teams have lined up and the national anthems are underway. Not the most rousing rendition of either anthem and there do appear to be some empty seats in the stadium. Let's hope the rugby gets the passions going, kick off by Giteau coming up now.

Big problems for the Aussies already, as from the first attack South Africa drive into them, first through Fourie and De Villiers and then a couple of pick and drives from The Beast. They are saved from further pressure in their 22 by an obstruction and get the chance to clear. South Africa look threatening already.

TRY Already, South Africa assert their dominance attacking from halfway, first the forward drive up making yards each time, then the backs are brought into play and the Australians are forced to kill the ball out wide. A quick tap and go from Du Preez cuts through the Aussies and he scores to mark his 50th cap.

Again, Brown palms a kick into touch for a South African lineout in Wallaby territory. Australia are giving the Springboks a platform here and putting themselves under enormous pressure.

TRY The scrum was solid enough, without making any ground, but the simplest first phase try as Du Preez releases Fourie who picks a nice line but the Wallaby defence was nowhere. Comedy miss from Steyn from in front of the posts, and that's about the first thing that has gone right for the Aussies.

He's missed this one and that's unfortunate, because it is looking like it could turn into a bit of a procession for South Africa and Australia need to do something to counter that.

Penalty against Australia in the scrum, it's the halfway line but Steyn will have a shot. If Australia don't secure their ball in the scrums, it spells more trouble for them.

Attacking intent from Australia, or a lack in faith in Giteau's kicking, as Giteau puts a kickable chance into touch for an attacking lineout.

The next Wallaby attack also ends with a turnover, as the man is stripped. After trying an attack down the short side, Steyn kicks long but it's straight out. However, Australia lose their lineout ball.

Now Giteau will have a shot at goal as South African hands in the ruck concede a penalty.

The Wallabies work a number of phases using Rocky Elsom, George Smith et al to drive the ball up the midfield. Steyn doesn't get himself away from teh wrong side of the ruck and concedes a penalty.

He puts this one over and that will be a relief, if he hadn't then Australia may have felt their options for taking points a bit limited.

Steyn misses the kick.

Steyn can't miss two of these and pops over the easiest of conversions.

A free kick from the lineout relieves them and a low driven kick gains them a lot of territory, giving South Africa a defensive lineout exactly on their 22.

The kick is over and that's halftime. The Springboks go in with a mere 16 point lead.

South Africa haven't been completely clinical and have made a few mistakes. However, their power and aggression has been way too much for Australia and they are good for that lead. Australia have not been at the races, unable to compete in a lot of the areas the game has played in and making frequent costly mistakes to put themselves under even more pressure. They will need to turn it round quite dramatically in the second half just to compete.

TRY A loose clearance goes straight to Elsom, who charges back into the South African defence, he has been the most threatening of the Aussie runners. From the ruck, a penalty, which is taken quickly, and Giteau slices through the South African defence and with three tacklers on him, reaches to plant cleanly across the line.

Better from the Aussies, who are looking to build on this start to the second half. They are in the South African half and going through the phases. The difference now is they are making some ground and committing defenders.

Turner has a dip at running the ball back from the South African clearance. Again, it is forced forward in the tackle but he made ground and looked threatening.

A bit of kicking and unsurprisingly, South Africa come off better, although surprisingly it is a long kick from Pietersen that finds touch in the 22.

TRY This time Habana goes over with no mistake. From the scrum, Fourie makes the dummy run, draws Giteau, and Steyn releases Habana at pace through the gap. Lovely move, four tries, the bonus point for South Africa if they win.

Lineout on the South African 5 metre line. Can Australia get back into this game? No. The lineout is stolen by Matfield.

Australia do seem to be establishing some dominance in the scrum. South Africa pull it down and are penalised, the Wallabies call for the scrum again.

Australia are still going. No they're not, after 15 phases the ball pops out the other side and South Africa's defence lasted longer than the Aussies' ability to not make a mistake.

It is South Africa's turn to put some pressure on in the opposition 22, but after a enat lineout move the ball is knocked on by the sub, Jacobs.

Steyn knocks it over and Australia are running out of time.

A kick straight into touch by O'Connor, who is looking a bit bruised. The later it gets, the more Australia are having to try but they are looking tired having been chasing the game from the early stages.

TRY Lockie Turner saves Australian legs with a giant kick down the touchline, that rolls into touch in the South African 22. The throw-in is not collected and Cooper cuts into South Africa before spinning the ball and Giteau takes a neat inside pass to put the ball down under the posts.

Australia showing some mongrel here and they haven't given this game up for dead just yet. They are running the ball hard and still trying to take the game to the Springboks, it may be too little too late, but they are still competing.

TRY Straight through the middle of the South Africans. Several more phases from Australia before the ball goes back to Lachie Turner, who accelarates quickly and darts his way through the disintegrating ruck. I don't think a hand was laid on him.

Giteau converts and that is the last kick of the game.

The margin in the end is only 7 points, and the Australians manage to score 3 tries themselves. However, the game never felt close and Australia were always chasing having conceded those early tries. Having said that, there was some promise from them in the second half when they took the attack to South Africa and managed to apply some pressure of their own.

South Africa were not at their efficient best at all times, but they were powerful and direct and were very hard to live with, especially once they were out front and a platform to build on.

These teams meet again next week at Brisbane, as Robbie Deans will see if he and Australia can salvage something from this campaign. South Africa, on the other hand, will be looking to seal the Trinations. Please join us for that and thanks from me, Jamie Allaway, for following this game with Scrum.com.