That quartet played 120 minutes in Denmark on Wednesday, which persuaded Postecoglou to field new signing Carl Starfelt despite 26-year-old having just been released from a 10-day quarantine.

The Swede suffered a tough debut, starting by being beaten by Josh Ginnelly all too easily for the opening goal. But he could have been the hero for Celtic, with Craig Gordon denying him an equaliser with a spectacular save.

Former Hearts manager Craig Levein was left umimpressed. "I look at Starfelt, and okay it's his first match, but he's not a dominant centre half," he said on Sportsound. "Boyce beat him in the air in the first half half a dozen times.

"What kind of centre back is he going to be? Is he a ball playing centre half - I didn't see enough of that. Has he got pace, no - Ginnelly burned him two or three times down the side in the first half.

"Compare him to [Hearts'] John Souttar, and for me it's just night and day. John's got pace, he's a good passer, he's good in the air. Things that you can see in one match."