The Swede, a summer arrival from Rubin Kazan, took a while to get going in a Hoops shirt and endured a difficult start, not least in his debut against Hearts back in August 2021.
That 2-1 defeat at Tynecastle seems a long time ago now, though. Starfelt is part of a Celtic team in the driving seat for the cinch Premiership title and a shot at a domestic treble. His fortunes have changed significantly.
"It was normal that we didn't play our best at the beginning of the season,” admitted Starfelt. “We brought a lot of new players in and some of them didn't get a pre-season. There were also a lot of players coming in from a lot of different countries and there were different coaches.
"So it was normal it would take a bit of time for us to adapt and also learn how to play with one another.
"Everyone has now adapted very well, we feel a lot more stable in our performances at the moment.”
So much of that is down to Postecoglou. "The manager has been really great to me,” Starfelt continued. “The biggest thing is that he's so clear in what he wants from me.
"When we go out onto the pitch, everyone knows what's expected of them.
“That goes for the whole team and not just for me personally. I also feel that he believes in me a lot, I'm really happy about that."
Starfelt has built up a strong relationship with fellow centre-half Cameron Carter-Vickers. The American is only contracted until the end of the season on loan – talks are reportedly ongoing about a permanent deal as Celtic are keen on activating their option-to-buy clause – and Starfelt said that he is full of admiration for the robust defender.
"Cameron has been a very good player for us and I enjoy playing with him a lot,” added Starfelt. "It is not my decision as to what will happen there but we will wait and see.”