Celtic star Kyogo could miss this weekend's game against Rangers through injury.
Ange Postecoglou admits the Japanese striker faces a race against time to prove his fitness ahead of the sixth and final derby encounter of the season.
The Hoops will make the short journey across Glasgow to take on Michael Beale's side at Ibrox this Saturday.
They will travel as champions, having already clinched the Premiership crown on Sunday with their 2-0 win over Hearts.
As the first goal went in at Tynecastle, scored by Kyogo, the 28-year-old appeared to hurt his shoulder after a tumble off the pitch.
He was soon subbed off by Postecoglou, with the striker clearly feeling in pain with it.
And it would appear the recurring issue could keep Kyogo out of this weekend's game versus Rangers.
Postecoglou said: "He hurt his shoulder a little bit. Hopefully, it's not too bad. He's had a few issues with it. We will just see and speak to the physios."
Celtic still have much to play for this term despite having already wrapped up the title.
On June 3, they will face off against Inverness at Hampden to decide the Scottish Cup final, which could well seal another treble for the club.
And, despite their status as heavy favourites to overcome Caley Thistle, the manager says sustaining momentum is crucial ahead of a day where Celtic could complete an unprecedented eighth domestic treble.
“That’s what I’m talking about,” he said. “I don’t think that’s in my control: the players will do that themselves. I know they will come in this week and I know they are going to train like they have all year. We will tackle these four games the way we have tackled everything else.
“We’ve got a cup final to prepare for and the best way to prepare for that is to be in really good form. I'm sure they all want to play in the cup final and they are only going to play if they are in good form and taking their opportunities. We won’t change our approach.
“I think the last four or five weeks you can feel the lads have kind of tightened up in the way we are playing, knowing what’s at stake. We haven’t been as free-flowing as we were earlier in the year, which is understandable. And it’s felt like a long year because of the Champions League and the World Cup break. But I’m in no doubt that in the next training session they will be out there working as hard as they always have.
“We want to win, mate. I’m going to put teams out to win. That’s it. And the guys respect that, that’s what they want. They don’t want to be given anything they want to earn everything they get. If they play they will play because they have earned it. If I make decisions that go away from that there will be other guys asking questions as to why they’re not playing.”
