Celtic winger Sead Haksabanovic suffered an injury blow against Hibernian.
The Montenegro international, who was starting his first game for several weeks, limped off 22 minutes into the clash in the capital.
He went down with an unidentified injury which ended his evening.
Before the match, Postecoglou provided an update on the injury status of Alistair Johnston.
He said: "He trained today and that was his first session. He won't play tomorrow, but all things being equal, if he gets through sort of the rest of the week's training then he should be available for the weekend's game.
"We'll just see hopefully getting him some game time in the weekend and then assess it from there.
"He's worked really hard, obviously with the cup final in mind to try and get back and he's got back really well and he's worked hard with the medical team and he looked after himself really well.
READ MORE: Celtic winger Sead Haksabanovic's mixed Hoops career so far
"It was good to see him training today and just good to have him part of it because he's obviously been a big part of it in the second-half of the year."
He also detailed the type of test of he was expecting from Hibernian.
"Well, like I said, I think all the games probably apart from ourselves and Rangers, everyone else has got something to play for," he continued.
"Like I said, with Hibs having Europe in mind it should be a good game for us. It is always a difficult game at Easter Road and it's always a good atmosphere and because they got something to play for, I think it'll be a good challenge for our guys.
"I think they've they've sort of been the most consistent they have been probably all year in terms of the way they're playing.
"It'll be a good challenge for us, it will be a good atmosphere and we are looking forward to the game.
"We are just kind of having our normal processes after a game and then just sort of preparing for this week.
"We know it's going to be a busy week with three games in a week and from that perspective it is just about making sure the boys are in a good sort of physical mental shape and just keeping training nice and sharp and getting ready for for the cup final in a week's time."
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