Thompson, who is a regular starter at club level with Melbourne Victory, is under no illusion over to the part he plays in the national set-up.
His seven appearances this qualifying campaign have been as a second-half substitute and, in five of them, Australia was chasing a goal.
"That role I've taken on board a long time ago," he joked on Sunday. "I feel like I've been a sub for 10 years with the Socceroos.
"Obviously, (coach) Holger (Osieck) sees me as a player that comes on and can spark something.
"Hopefully, I don't have to do that on Tuesday because the game's already sewn up by then but, if needed, I'm willing to do the same again."
His impact was no clearer than in Australia's 4-0 rout of Jordan last week, his first touch after coming on as a 60th-minute sub resulting in Tim Cahill's ensuing goal to put the Socceroos 2-0 up.
On Tuesday, Thompson will get the chance to earn his 50th cap for Australia as the Socceroos attempt to qualify for a third successive World Cup with a victory over Iraq securing second spot in their group and a ticket to Brazil.
"It would be pretty special for me if I get on the pitch, get my 50th and we make the World Cup," he said.
"It seems as though the moons would align for me. It would be an amazing achievement if that happens."
Of his 49 matches so far, Thompson rates his appearance away to Iraq in October last year as the highlight.
He replaced Alex Brosque in the 75th minute then went on to score the winner in the dying stages of the 2-1 victory.
Level with Cahill on 28 goals, Thompson is just one away from reaching Damian Mori's all-time scoring record for Australia.
With 13 of Thompson's goals coming in Australia's 31-0 dismantling of American Samoa in 2001, many feel Cahill is more deserving of breaking the record.
And Thompson isn't disagreeing.
"American Samoa are a world-class team - I'd like to see him put 13 past them," he joked.
"Thing is is Timmy has been an unbelievable player for Australia for so long so, for him to score and maybe even surpass Mori's record, that would be amazing because he definitely deserves it."