Mulgrew is the favourite for the accolade after yesterday being named on a shortlist with Steven Davis, Jon Daly and Dean Shiels.
Mulgrew has had a remarkable season: most of it hugely rewarding, but one part truly awful. His father, Charlie Sr, passed away in November, prompting Celtic supporters to display a banner saying "The Mulgrew Family Never Walk Alone" while their player grieved. That loss was the one dark episode in a campaign which otherwise has been the most enjoyable of his career, bringing regular first-team football for Celtic, a league championship winner's medal, his first Scotland cap, and now the recognition of being voted one of the season's best by his fellow professionals.
None of that was imaginable when Mulgrew left Celtic in 2006 in part-exchange for Lee Naylor, having failed to hold down a place at the club where he had come through the youth ranks. Spells at Wolves and Aberdeen, via a loan at Southend United, followed before Mulgrew returned to Parkhead in 2010.
"I believed I would get back to this level but I didn't think I would get back to Celtic," he said. "You have to go out to make a career for yourself and do as best you can and keep believing in your own ability. I am thankful to get the opportunity to come back here, and things have gone well so far.
"Of course there are always moments of doubt but that's where you need good people around about you to keep you going and keep believing. My dad, who is not with us any more, played a huge part. My mum as well, and basically my family. Whenever I speak to them they are always positive but the person who played the biggest part was my dad. He won't be here to see it [the award nomination] but I'm sure he would have been really proud if he was.
"It's a massive honour to be nominated, I'm delighted. When your peers vote for you it's especially pleasing. It's great to be voted for by them so I'm very pleased."
Neil Lennon made his admiration for Mulgrew obvious by making him his first signing after taking over as Celtic manager two years ago. "A lot of players have excelled under him and he seems to get the best out of them. I think he's got the best out of me and I am thankful for that.
"My game's come on leaps and bounds. Big thanks have to go to the manager and the coaching staff for that. It's just about having belief and playing well and I feel I have played pretty well this year. You always think of what could have been, a treble and stuff, but you have to look back at the start of the season and the target we had then. We'd have taken the league above anything else."
Mulgrew has height, a certain level of composure, excellent dead-ball skills and consistency among his list of attributes, and it has been hugely to his advantage, too, that he can play in a variety of positions. This season he has often featured at left-back but there have also been stints in midfield and at centre-half. He feels comfortable wherever he is placed. "Coming through the ranks at Celtic I played in all positions from about 10 or 11 years old. I think a centre-half has to be able to head the ball and do the basics, but it is a bonus if you can see pictures from the back and be able to play football. It helps the team if you can build from the back, but you have to do the basics first and foremost."
Last season's PFA Scotland player of the year was Emilio Izaguirre, who was effectively the player Mulgrew had to displace from the Celtic team in order to further his own ambitions. Unfortunately helped by Izaguirre's serious ankle injury, but mainly because of his own improved form, he did so. "Emilio is a great player but I knew I could play in different positions. I spoke to the manager and he was aware of that. It was up to me to believe in myself and work hard. I got back in and I'm thankful I got the chance.
"But it would be catastrophic for me to think 'I've arrived'. You can't start thinking like that. As a team we will be looking to make inroads in Europe and looking to retain our title and have another good season. Hopefully, we can be in the Champions League next season. I know there are some qualifying rounds to come through, but every player wants to be involved. I think a lot of the players here haven't played in it, and if we qualify for that it would be a huge experience."
The PFA Scotland Player of the Year will be announced and presented at the players' union annual dinner in Glasgow, sponsored by Cheque Centure, on May 6.