The odds are stacked against City, who face Perth Glory on Sunday night in an elimination final for a place in the final four.
They've beaten top-six opposition just twice all season, the last being three months ago - a 1-0 win over Western Sydney Wanderers.
And City have losing form against the Glory - the latest of two losses this season coming last Sunday in a madcap 5-4 loss in Western Australia.
Despite the ominous record, Cahill and City are revelling in their role as championship spoilers.
The 37-year-old said the tag of underdog sat very comfortably with him as he began his first A-League finals series.
"I've been written off my whole life," he said. "I wasn't supposed to play at the last World Cup. I wasn't supposed to play at the Asian Cup.
"And I wasn't supposed to do well in the A-League either because I'm too old and I'm 37.
"I like it like this. We know what's on the line.
"It's good to be the underdog for once in the finals and not be expected to win this weekend or even the grand final.
"I can guarantee not many clubs will want us to beat Perth because that means they have to play us.
"In one-off finals they'll much prefer to play someone else."
Cahill says his record of 13 goals in 25 appearances, including the winner in the FFA Cup final, is evidence of a successful first season - and a reason for other teams to be fearful.
"In all the big games this year, I've shown up - in all the big games when it's counted," he said.
"That's pretty much what's happened my whole career."
The 5-4 loss was one of the craziest results in the A-League's history and Cahill said he'd "never played in a game like it ever" over his 20-year career.
He expects a very different match this weekend.
"It will be very interesting to see the way Perth play ... I don't think Kenny Lowe will ever set up again and be that brave," he said.
"He said he was going to come (to Melbourne) and test us out. We were happy to be tested and happy to react (in Perth)."
Defeat last week in Perth meant City lost the chance to qualify directly for the AFC Champions League through league position - a stated goal of the cashed-up City Football Group ownership.
Cahill said he hadn't closed the door on a back route into the prestigious competition through a successful finals series.
"I didn't realise that if you win the game, you've still got a shot at Asia, which is awesome," he said.
"There's so much to play for.
"It's a one-off game. We get to have another crack at the cherry."