The pair had been team-mates at Dundee United for two years, with Mair recalling Archibald as an easy-going figure and one of the "jokers" in the dressing room.
Nothing, however, brings about a change in a footballer's personality quicker than the switch from being a player looking solely after their own affairs to becoming a manager responsible for the welfare of dozens. Mair added to that when he became the third new face at Firhill this month and was followed yesterday by Chris Erskine, who has rejoined Thistle on loan from Dundee United until the end of the season.
Management is, by and large, a serious business and Archibald's transformation since succeeding Jackie McNamara almost a year ago exactly has been a reflection of that. The cropped haircut has gone to be replaced by a softer, slightly longer style. His nice-guy persona has been ditched when necessary too, Mair revealing that Archibald's reaction to Thistle dropping two points against Kilmarnock on Saturday was the first time he had seen his friend angry.
If those changes took Mair by surprise following the completion of his move from St Mirren, then the defender understands why that needs to be the case. Mair, just three years Archibald's junior, is also in the process of undertaking his coaching badges with a view to moving into management one day and realises that evolving as a personality is also part of the process.
"We were team-mates at Dundee United and I did the coaching A licence with him in the summer as well, so we've been speaking," said Mair. "Archie was a leader on the park and off it as well. He was a good guy and everyone liked him. He's a likeable guy - after the game on Saturday was actually the first time I had seen him angry.
"He's a nice guy but was upset that we had lost two points. You can see he's become a different character as a manager, you've got to. I've only been here a short time but you can see that he's changed. He used to be a bit of a joker in the dressing room and now he has to take himself away from that, be a serious man. It seems like he's adapting to it well."
Mair turned 33 last month but has designs on playing for several more years yet. He believes the tips he has learned studying for his A licence will help sustain him for a few years and felt more players would benefit from doing likewise earlier in their careers.
"I do watch games differently now," he added. "I used to watch games and say, 'look at that goal' and now I'm saying, 'look at how the defence moved there'. I pause games and rewind them and watch incidents again. I look at shapes and that kind of thing. It's what happens when you get older and get your manager head on.
"That's obviously what the gaffer's doing now that he's moved behind the desk. That's something I'll look forward to in future. But I feel like I've got a few good years left in me. Doing the coaching badges makes you a better player, I feel, as you have to explain certain situations, so you're talking about them. When you're explaining things to others it helps you understand it better, too. I'd actually encourage young kids to do their coaching badges early doors as you learn so much from it."
If Mair has any regrets about how his time at St Mirren ended then he is keeping those thoughts to himself. Used sparingly by manager Danny Lennon over the past year or so, the defender decided the time was right to move on, with Thistle giving him the opportunity for a fresh start. Instead he prefers to look upon the highlights, in particular St Mirren's Scottish League Cup win last season.
"I just look back on the four and a half years I had there and it was brilliant," he added. "I played in 149 games, in two cup finals, and won a cup. The reason I left Aberdeen was to play football and win a trophy and I've done that. I can't look back with any regrets but I'm not interested in St Mirren at all now.
"There were sniffs about me coming here in the summer but nothing materialised so I decided to stick at St Mirren and give it a try. I got back in the team, played well and still didn't keep my place. That made me realise it was time to go. When the chance came up again to come here I thought, 'definitely, I'm off'."
Mair will now look to help Thistle record their first home league win of the season this evening when St Johnstone come to town. "I hadn't been aware of the problems with the home form," he added. "We need to be a bit more streetwise."