Leckie hasn't played since February 24 because of soreness associated with earlier knee and hamstring injuries and then illness.
But Leckie and defender Curtis Good, who has also recovered from illness, are both available for City's vital home clash against the Jets on Saturday.
Coach Vidmar, who has been sick this week, may not attend the game as his seventh-placed City seek to make inroads into the top six.
"He is on the upward in terms of his health ... not sure at the moment," City assistant coach Raffaele Napoli said on Friday.
"We're in constant communication and preparation hasn't changed day-to-day pre-training, post-training, all those things have stayed the same, we're a very process-driven environment.
"So hopefully he's there, if not we will be in constant contact and we will try and get the result."
Leckie's return is a bonus for City, who start the round two points behind sixth-placed Western Sydney and fifth-placed Sydney FC.
But the Socceroos winger will be on restricted game-time against the Jets, who languish in 11th spot with only four wins this season.
"We won't be able to get greedy with him even though we'd love to," Napoli said.
"Looking at our next three games and trying to manage his load appropriately and his game-time and expose him and get some continuity into him because we know how important he is for the group.
"That's giving him every opportunity to succeed long-term, so that is a focus."
Napoli said Marco Tilio was likely to return from a hamstring injury next week but stalwart Scott Galloway had suffered a setback to his knee injury and would be sidelined for a "couple of more weeks".
"The more players we have available, the better - competition for spots is really healthy," Napoli said.
"That, historically, when we have been really successful, we have had that."
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