Qualification for the 2018 World Cup in Russia continues on Thursday and top spot is up for grabs in Group E when Syria and Japan meet in Muscat.
Syria are currently leaders in Group E with nine points but have Japan just two points behind in second place.
A win for Japan would see them move into top spot, but a loss could see Singapore move level on points provided the Lions overcome Afghanistan.
Japan are yet to concede a goal in the qualifying stage so far, scoring nine goals in the process, but were held to a 0-0 draw against Singapore in June.
Syria are also yet to concede in their three games, winning 6-0 against both Afghanistan and Cambodia respectively.
Japan coach Vahid Halilhodzic knows Syria will be a tough opponent and a loss will put them in a difficult position.
"The match against Syria is going to be most difficult and most important among the matches we had in this year," he said.
"They have a couple of good players and don't need so many goal-scoring opportunities.
"I watched about eight of the Syria matches, and I know each player's strength and weakness and the way they play.
"We need to get ready to win the battle. We've got excellent quality and experience. We will come out with confidence and keep winning."
Halilhodzic named 20-year-old striker Takumi Minamino in his squad and the Red Bull Salzburg man is expected to make his national team debut.
"Minamino always gets a goal on his own and positions himself at a place for his team-mate's goal," Halilhodzic said.
"He will be a very effective player for the Japan national team in a few years. I also want [Tsukasa] Shiotani and [Yosuke] Kashiwagi to make it their new start, showing different quality."
Japan have never lost to Syria – with seven wins and one draw – but this clash will prove to be the toughest of them all.
