Cahill's record 49th and 50th goals for Australia - including an extra-time victor at ANZ Stadium - earned the Socceroos a heartstopping 2-1 victory over Syria in the second leg of their play-off on Tuesday night.
Australia's hopes were then handed a significant boost three minutes into extra time, when Al Mawas was sent off for an apparent foul on Robbie Kruse.
The Syrian football team, which has been fighting for the chance to enter their first ever World Cup, has lost a crucial qualifying match against Australia.
Syria's improbable run toward a first World Cup attracted global attention, which heightened after it salvaged a 1-1 draw in the first leg last week at its adopted home ground in Malaysia.
Another wrote: "37 years old, playing 120 minutes of World Cup action - and bagging 2 goals in a must-win match?"
Milligan added: "I think the next round will be a different type of match, they're going to present different challenges".
But Hertha Berlin winger Mathew Leckie, 26, engineered parity for the hosts when he provided the flawless cross for former Everton midfielder Cahill's first on 13 minutes.
Once Al Mawas was sent off for a second foul on Aaron Mooy four minutes into the first period of extra time, it appeared only a matter of time before the Australians would break down the already tired visitors.
Anas Ammo of the Syrian Network for Human Rights told ESPN that at least 38 players from Syria's top division of the Syrian professional leagues and dozens from the lower divisions had been killed by the Syrian government.
With the CONCACAF qualifiers coming to their conclusion tonight, Australia and Tim Cahill will not have to wait long before learning their fate.
Syria threatened with an early counter-attack and it was a warning Australia failed to heed, as they gifted the visitors the lead in only the sixth minute. The Aussies will face the fourth-placed side in the "Hex", with USA, Panama or Honduras all potential opponents for them next month.