Western United can haul themselves off the canvas and pull off a mighty comeback against Melbourne City to reach the A-League Men grand final, says coach John Aloisi.

And he is adamant star striker Noah Botic will be fit again to lead that charge.

United trail 3-0 after Friday night's first leg at AAMI Park, with everything to play for - a grand final berth against Auckland FC or Melbourne Victory - in next Saturday's away fixture at the same venue.

"I'm sure that they will be upset like I am, but we've got seven, eight days now to make sure that we get them believing again and try and make a hell of a game next week to turn it around," Aloisi said.

"They've done it in the past, we've been down in games in the past, and we've been able to come from behind. So that's clear that we can do that."

Western have scored four goals or more six times this season, and at least three goals 12 times.

"The motivation will be that we believe at our best we can beat anyone," Aloisi said.

"We can't look at we have to score three goals, four goals. We have to look at how do we perform to win the football game?

"A lot of the time this year when we've performed like that - for instance, away to Auckland - we ended up scoring four goals.

"So we've done it, we can do it, we know that, and now it's preparing right to be able to do it."

Botic played just 19 minutes off the bench after he and United were reluctant to risk a quad injury he suffered against Adelaide United.

"I think that another eight days, he'll be fine to start next game," Aloisi said.

"We know that he's been playing well and scoring goals and confident, so we expect him to be the same next week

"If we get those chances, I'm sure that Noah will score."

City are ready for everything United will throw at them.

"They're gonna come at us for sure, 3-0 up," winger Marco Tilio said.

"But we'll take it on as every other game, and the same way we did tonight, and just be cautious in terms of they're gonna have to come out with everything."

Coach Aurelio Vidmar is determined not to let his side invite pressure.

"Finals football's completely different. Everyone's more on edge," he said.

"We had Zane (Schreiber), Ale (Lopane), Maxy (Caputo) playing their first finals and it's a different vibe. It's a different feel.

"You can invite your own pressure because it is a final, it is a semi-final, and you can overthink it sometimes, but they've done so well through the course of the year."

City expect to regain Nathaniel Atkinson for next Saturday's game.