When the news came through that Kenny Miller had retired from international football he was in the dressing room at Nottingham Forest. Much footballers' chat goes in one ear and out the other, but not this.
Mackie liked and admired Miller but inevitably his instinct was to regard any striker's withdrawal from the Scotland scene as a potential opportunity. Leigh Griffiths, Jordan Rhodes, Ross McCormack and Shaun Maloney are also in the squad for tomorrow night's World Cup qualifying tie against Belgium and the game in Macedonia on Tuesday. But Rhodes and Mackie are the two best suited to playing the single-striker role vacated by Miller, at least until Steven Fletcher returns to the side.
Mackie was in manager Gordon Strachan's first squad - for the February friendly against Estonia in Aberdeen - but did not play and has yet to be capped under the current manager. The games against Wales, Serbia, Croatia and England passed him by. Being detached from the group meant Miller's decision came as a shock to him. "I was greatly surprised. I didn't have any dialogue with Kenny so I didn't know his thought process. After seeing him score a fantastic goal at Wembley, and also how well he played overall, plus how he has done anyway for Scotland, I was stunned when the news broke while I was in the dressing room at Forest.
"It was a complete shock to me. More so because I hadn't been in Scotland squads and got a sense of anything. To me it had just seemed that Kenny was going along very well and as fit as ever.
"Football goes round in circles, doesn't it, and now it's come all the way back round for me. I've got an opportunity now to stay in the squad. That's what I want to do and hopefully it works out that way for me."
Mackie doesn't have Miller's high-level experience or knack for delivering occasional, exceptional goals, but there are similarities in their style. Both rely on energy, work-rate and a bit of pace. Mackie - born in Dorking and eligible for Scotland because of a grandfather from Kilmarnock - isn't short of enthusiasm or confidence.
"It is a big challenge for me to try and fill Kenny's boots but I'm definitely not here to be like anyone else. I'm not going to pretend to be like any other player. I'm here to be myself. If the manager sees the qualities in me that I can be similar to Kenny then that's great for me.
"I definitely think I can play up front on my own. I've got a lot of energy in my game, I can make runs in behind; I can come and hold the ball up. It's a position where you can be frustrated because there can be long periods without possession, especially against top sides. But having played in the Premier League the last couple of years there are a lot of games where, when you are in lesser teams, it can be similar to what happens with Scotland."
Until the announcement of this squad, Mackie's worry wasn't about whether he could play up front on his own, but whether he would play for Scotland at all. He fell out of the team under Strachan last season as an inevitable consequence of playing fewer games for his club, QPR. He was one of victims of the club's chaotic management as they finished bottom of the Barclays Premier League last season. Manager Mark Hughes signed 11 players in the 2012 summer window and then his successor, Harry Redknapp, added five more the following January.
Worse, there were widespread claims that the QPR dressing room was split into cliques, with major issues between the players over their different wages and the perceived lack of commitment from some. QPR won only four of their 38 league games.
"I felt that at the time they [a section of his team-mates] were maybe playing on the back of reputations," said Mackie. "Not just last season, but also the season we got promoted, it was a fairly hectic environment to work in. There was always the club trying to get names in, to get players in when there was already a lot of players there anyway. Good players. There was an element of thinking 'we can't keep just buying players in, there's already enough good players here'. But it was the way they went. They went to buy a lot of players and, like I say, it was a bit hectic.
"I did speak to Harry. I don't like coming in and being paid for not playing. I want to work hard for what I get. I want to be out there playing all the time. Harry was brilliant with me in that respect. He gave me the truth. He said he was looking to buy players and that my game time was going to be limited. So I couldn't ask any more from Harry, apart from the fact I hardly played last season. Harry Redknapp was great for me, great with me. When I left he wished me good luck.
"But it was the most frustrating time of my career to date. It was still very frustrating for me the latter part of last season being stuck on the bench, especially when we weren't doing great as a side. I wanted more game time. I feel the writing's on the wall for you as a player when the team's really struggling yet you still can't get a game and you're stuck on the bench."
He was moving towards becoming a forgotten man at QPR until making his escape at the end of July. Nottingham Forest paid £1m to take him north. The rewards have been swift: six appearances for the club in August and, tomorrow night, a cap to take him into double figures for Scotland.