The former Anfield player admits his loyalties will be split on Wednesday when the two clubs meet in a pre-season friendly, having spent seven years with the Reds during the 1980s
The former midfielder made 190 appearances for the Merseyside club between 1981 and 1988 and famously scored a goal in Liverpool's 3-1 victory over rivals Everton in the 1986 FA Cup final.
But, despite a superb career in England, Johnston has always called Australia home and that is why the 53-year-old will be hoping Liverpool are not victorious at the Melbourne Cricket Ground on Wednesday night.
|25/1||Melbourne Victory are 25/1 with Paddy Power to beat Liverpool 1-0 on Wednesday
"Merely because it is not a league game, it is a pre-season friendly and this is [Victory's] Cup final."
The friendly will mark Liverpool's first match on Australian shores and a key part of the club's pre-season as they attempt to build on their seventh-placed finish last season.
Liverpool started their close-season preparations with an impressive 4-0 victory over Presto earlier in July and flew into Australia on the back of a 2-0 win over an Indonesian XI in Jakarta on the weekend.
Johnston urged the Liverpool players to continue their fine recent form and embrace the big crowd. which is expected to be in excess of 95,000, in Melbourne.
"I said to [the Liverpool players] three or four months back that they are in for a treat wherever they go around the world," Johnston said.
"They have just been in Indonesia with big crowds, but this is a very knowledgeable football audience in Melbourne. They have never been to the MCG, which is the home of football in Australia.
"When that song 'You'll Never Walk Alone' strikes up they say it will be 92,000...everyone of those people will know every one of those words. So hopefully it will be a fantastic game."