Asian champions Japan can become the first side to qualify for the 2014 World Cup with victory in Jordan on Tuesday, while South Korea, Australia and Uzbekistan are odds on to score home wins and clarify the crowded pool picture.
The Blue Samurai thrashed Jordan 6-0 at home in June, a result that has helped them establish an eight point lead over Australia, Iraq and Oman in Group B.
But Tuesday's clash in Amman will be a tougher prospect without the key duo of playmaker Keisuke Honda and attack-minded fullback Yuto Nagatomo at a venue where Jordan were able to humble Australia in September.
A 2-1 friendly win over Canada in Qatar on Friday involved some sloppy errors by Asia's best side and the players know improvements are required to see off Jordan, who have bounced back well from their Saitama rout.
"If we play like we did in the first half against Canada then things could become very difficult for us," playmaker Shinji Kagawa said after the win over the North Americans.
Shinji Okazaki should start after scoring the opener against Canada with the VfB Stuttgart forward demanding big improvements ahead of the decisive qualifier.
"It is good that we have got this game out of the way because we can't play like we did (against Canada). We allowed our opponents to create a good shape and we have to take a good look at ourselves about that," he said.
Japan might only need a draw to qualify should Australia and Oman draw in the earlier Group B clash in Sydney.
That result is a strong possibility as the duo, along with Jordan and Iraq, have all taken points off each other in a number of defensive-minded, slow tempo clashes. The quartet have each scored only four goals in the group.
The Socceroos remain favorites, though, to grab the runners-up spot and the other Brazil berth from the pool as they have a game in hand on their rivals and host three of their remaining four matches.
New York Red Bull striker Tim Cahill is expected to lead the line and the former Everton player has called for a high-tempo display, something that was lacking in a drab 0-0 draw when the teams met in muggy Muscat in June.
"I know the international game can be a bit more relaxed, slow tempo (compared with club soccer), but this game has to be high tempo from us and we have to make sure we pressure them and make them feel unwelcome in our stadium," Cahill told reporters.
"They'll be under pressure to get a result, so they'll play very deep.
"We have got pace on the wings with Krusey (Robbie Kruse), Brosquey (Alex Brosque), Brett Holman and other options so we will look to them to get a lot of crosses into the box."
In Group A, South Korea and Uzbekistan can put daylight between themselves and the chasing pack if they claim expected victories at home to Qatar and Lebanon.
The Uzbeks, who lost 2-1 to the United Arab Emirates in Asian Cup qualifying on Friday, top the group with eight points from five games, with the Koreans a point back but having played a game less.
Qatar have seven from five games, as do three-times Asian champions Iran who are the most likely to prevent the top two from going to Brazil but are not in World Cup action on Tuesday and instead face Kuwait in an Asian Cup fixture.
The Qataris will be led by Fahad Thani for the Seoul clash, the 2022 World Cup hosts fourth head coach of the campaign as they bid to qualify for a first finals.
Qatar lost 1-0 away to Bahrain in Asian Cup qualifying on Friday but Thani remained confident his side could get something against the perennial World Cup qualifying Koreans, who thrashed the West Asians 4-1 in Doha in June.
"This result will not affect us going into our next match. We know the importance of the next match," Thani said after the defeat in Bahrain.
"We have appropriate plans for our next clash. Hopefully, we will get a satisfactory result."
(Reporting by Patrick Johnston, editing by Justin Palmer)