This recognition, of a player who cared about improving, bound Rae to the young defender.
MacKenzie was a teenager then, when he and Rae played alongside each other in the Rangers reserves, but there was something in his mentality and the potential of his 6ft 4in frame, his pace, his distribution, that resonated with the older player.
When Rae took charge of Dundee in 2006, he asked MacKenzie to move to Dens Park, too, even although the centre-back still had one year left on his contract at Ibrox.
“He was more interested in first-team football; he was getting a bit frustrated,” Rae says. “That tells you a little bit about him because he’s a Rangers fan, so to walk away from there was a big thing. He was more interested in developing and he played over 100 games at Dundee.”
Rae does not need to be vindicated for the faith he showed in MacKenzie, but the player’s Scotland call-up still represented confirmation that the pair were right to trust in their instincts. Rae was certain enough of MacKenzie’s potential to recommend him to Paul Ince when the pair were working together at MK Dons, with Ince signing the defender last year.
Now 26, and having adjusted to the greater pace and ability encountered in League One, MacKenzie has begun to thrive. Even before his elevation to the Scotland squad, he was attracting enough interest from Championship clubs for MK Dons to extend his deal.
“The first season he went down, he was up against better strikers, guys like [Craig] Mackail-Smith and Lee Hughes in League One, so it was a development,” Rae says. “But I’m led to believe that he’s at the top of his game at the moment, because I’m still in contact with Karl Robinson, the MK Dons manager. He’s got really good attributes and there’s not many players like him about, because he was well schooled at Rangers.
“[Moving to Dundee] was about his development, because youth and reserve football is good up until a point, but you need to start testing yourself. He needed to learn the game and he’s now developed into a very good centre-half. He was always a boy who struck me as someone who cares. He always wanted to develop and mature, so was often his own worst critic. That’s good, though, because it drives you on to better things.”
MacKenzie will need to make a similar impression on Craig Levein, since his Scotland experience will be limited to a series of training sessions and, at best, a short spell during the game itself. Yet Rae believes he can at least reassure the Scotland manager that he is worth monitoring over the coming months.
MK Dons are fourth in League One and MacKenzie has become central to their hopes of promotion. Scotland are also short of options at centre-back, where Gary Caldwell and Christophe Berra -- playing regularly in the Barclays Premier League -- are the established pairing, with Grant Hanley and Danny Wilson -- on the fringes at Blackburn Rovers and Liverpool -- next in line.
The form of MacKenzie, though, is a reminder that players outwith the top-flight are still worth considering.
“If you look at Wales, Northern Ireland, the Republic or some of the Scandinavian countries, they all have players in League One,” Rae says. “Some of those have a higher rating than Scotland, so because you play at that level doesn’t mean that you should be written off.
“Gary’s a good age, so it’s just a case of him trying to impress in the short time that he has. It will also give him an opportunity in terms of bigger clubs coming to have a look, because a lot of people wouldn’t have known about him. Coming to Dundee was a backwards step to go forward again, and this is the next step in his career.”