Sitting front and centre in the audience, enthusiastically applauding the presentation of the trophy from the SPL sponsors, the Clydesdale Bank, was Gordon Strachan, the manager who had decided the then 20-year-old would have to leave Celtic if he was going to find his way to the top in the game.
The presence of the former Parkhead boss seemed to serve as some kind of validation that Mulgrew was indeed now the real deal and, indeed, no-one is happier to see a young man turn his career – and life – around than Strachan.
But, perhaps as a result of the journey he has had to negotiate to this point, Mulgrew recognises better than most how fickle this game can be.
If he needs any more reminding, he only has to cast his mind back 12 months when it was Emilio Izaguirre who made a clean sweep of the Player of the Year awards.
It was fitting reward for the Honduran defender's stellar first season at Celtic, and promised to be the launchpad for even better things this season.
However, a serious ankle injury sustained in only the second game of the campaign has virtually wiped out the opportunity to build on Izzy's initial success.
On a number of occasions, Mulgrew stepped into the breach left by Izaguirre's enforced absence, but it was when he moved into central defence that his season really ignited.
But the unhappy experience of Izzy's follow-up season has served as a salutary lesson to Mulgrew, who is already anticipating another fight just to hold his place in Neil Lennon's starting XI, let alone a defence of his Player of the Year awards.
He said: "Emilio was unfortunate with injury at the start of the season, and I managed to take my chance when I got it, playing in a few different positions. It shows how unpredictable football can be, and I'm just thankful the way the season has gone.
"Who would have thought that, after getting all the awards, Emilio would not have played for a full season, near enough?
"You just can't look too far ahead. You have to keep focusing on what you are doing and be prepared for each match and, hopefully, get a bit of luck."
Mulgrew would like to think that good fortune will extend to Izaguirre, even though his return to full fitness and form will put further pressure on places in the Hoops defence.
With Jaroslaw Fojut already signed on a pre-contract agreement, and Glenn Loovens, Daniel Majstorovic and Cha Du-Ri expected to join Mark Wilson in leaving the club, the revamping of the defence is moving on apace.
Mulgrew will be ready to fight his corner, and welcomes the bonus that having a player like Izaguirre back to his best will bring.
"He's a big player for us, and we're all happy to see him back, and I'm sure he will already be looking forward to next season," was his take on Izzy's return.
Another consequence of the movement of older players out of the club is that Mulgrew suddenly finds himself one of the more experienced men in Lennon's squad.
That brings a smile to the face of the 26-year-old, who said: "I have quite a lot of exper- ience now, and I'm sure the manager will look to me to give a bit of guidance to the younger players now.
"I never thought I'd ever say that because I always saw myself as a young player. But I have to take that responsibility."
Lennon has already acknowledged Mulgrew's qualities in this regard by handing him the captain's armband on occasions when Scott Brown has been absent.
"It's a great honour to captain Celtic, and it does show he has belief in my ability," is the defender's proud take on that.
Like the plethora of Player of the Year awards, it was something which no-one – including Mulgrew himself – could have envisaged when he was being allowed to leave Parkhead six years ago.
Mulgrew is philosophical as he considers the detours through Wolves, Southend and Aberdeen which have led him to this point.
His relationship with Strachan appeared to come to a head in Krakow during a pre-season game in which he was pulled off before half-time.
It's not a moment he is happy to revisit, and when invited to do so, he deftly broadened the discussion.
"Is there anything I would have done differently?" he mused. "No. Sometimes things happen in life and you learn from them.
"I got taught a big lesson when I left here and played with smaller clubs than Celtic and you appreciate what you had here. It made me stronger as a person moving away from home. It made me grow up."
Pushed again on what exactly happened in Krakow, when he and Ross Wallace chose not to go into the dressing room at half- time but stayed instead in the dugout, Mulgrew remained firmly behind his defensive position.
"Listen, a lot was made of it, but there wasn't really much in it," he insisted. "It was just one of those things. Someone gets a hold of it and it gets blown up.
"Gordon Strachan was tough with his young players. But that's just the way it goes, and sometimes you need to move on and learn and come back."
All of which Mulgrew has successfully done. And, having reinvented himself, there will be no resting on any laurels during the close season.
Mulgrew is already planning how he will get even better and revealed how he plans to make this happen.
"You just have to prepare yourself right over the summer," said the man who will sign off this campaign with Sunday's final SPL game against Hearts before he collects his championship winner's medal.
A trip to America, where he hopes to gain his second Scotland cap, will bring the curtain down on a year to remember, and he added: "Celtic have some early Champions League qualifying fixtures, so you must make sure you are ready for them.
"But you have to make sure you have a rest, and give your mind a rest, more than anything else. As champions, I'm sure we will be a scalp to a lot of teams in Scotland, but we always are, anyway.
"It's going to be tough, like every other season, and the competition for places is going to be tough, too. So it should be at club like Celtic. Players should be pushing each other all of the time."
In his case, no-one more so than Mulgrew himself.