IT is pretty routine for a top-class manager to watch a match and pick up on something that goes over the heads of the rest of us.

That normally involves some tactical or positional subtlety, or a strength or weakness some player might have. Yet when Gordon Strachan sat through a recording of Scotland's last match against Wales, he had a thought that would not have occurred even to another coach, because it was uniquely relevant to only him. Namely, if it had not been for an assistant referee's mistake in that match he would not now be the Scotland manager.

As he held court before the return fixture against the Welsh at Hampden this evening, Strachan reflected on a pivotal moment from that meeting in Cardiff in October. Scotland were 1-0 up when Charlie Adam crossed into the goalmouth and Steven Fletcher buried a header for 2-0. At least, that is how it would have been recorded if Adam's bending cross had not been wrongly judged to have gone out of play on its way to the goalmouth.

A 2-0 Scotland lead could have been successfully defended, there would have been a precious victory or at very least a draw (if Gareth Bale had still scored twice) and Craig Levein might have been permitted to last longer in the job. Instead he lost in Cardiff, then in Belgium, was sacked, and a vacancy opened for Strachan. "I might not be sitting here but for that," he said. "At some stage I would like to have been sitting here. But I would rather we had won the three points."

It was a reflective line of thought from a man who will take charge of his first competitive game as Scotland manager tonight. Strachan reeled off some tales about following Scotland on the terraces as a much younger man but there was no need for him to prove his credentials. He has a profound understanding of how the results he delivers can affect the mood of the entire country. Maybe not tonight, at the resumption of a World Cup campaign in which Scotland are bottom of the group and horribly adrift of leaders Belgium and Croatia after four winless matches, but certainly as the fixtures unfold in the months ahead.

"The realisation, when you are the manager of Scotland, is that this is fantastic," he said. "You have the opportunity to make a nation happy. Before, for me, it was always a certain amount of people at Coventry, Southampton and Celtic, which was bigger, obviously. With Scotland, you can make millions of people happy, but the problem is you can make a nation miserable at the same time. The rewards are fantastic but there is another side to it. You can make people miserable as well.

"The fans have stuck with team [over the years] and they do it in a way that is different from everybody else, apart from Brazil maybe, and it is easier for Brazil's fans to turn up because they are winning every flipping game. I've been to a number of World Cups and European Championships through television and there's no doubt that, although the Irish have stepped in, they are not as good as us at the celebration thing."

For all his cantankerous reputation, Strachan likes a laugh, and a few were provided by the comments of Mickey Thomas and John Brown this week. Thomas, once a team-mate of his at Leeds United, had coughed up a line about this being the worst Scotland team ever. Strachan likes Thomas, and couldn't contain his grin: "To validate his statement, I think Mickey would have to be 150 years old, to have seen every Scotland game in the last 130 years. I'd need to look at his passport and if it says 150. I think Mickey is the only man who could get a passport with 150 on it." Thomas was jailed for 18 months for his role in a counterfeit currency scam.

As for Brown's suggestion for dealing with something just as dangerous as prison – Bale in full flow – he was equally amused. A player can't run without legs, Brown had said, as if wiping the blood from his lips. "I don't think that is going to happen these days. The days of 'Chopper' Harris are gone."

Without anyone like Chelsea's legendary old enforcer, then, how did Scotland intend to suppress Bale? "We have an idea. We have contingency plans for the whole team. If one man moves there, then someone else has to move there. I just like watching good footballers and today's surfaces, rules, and everything else means that people like to see the top players in the world play and have space without being kicked out the game. I've had a shape in mind for a long time and now I've settled on my team. I know which way we want to defend."

The players will be told the side this morning. There were no clues, although he dismissed a suggestion that Gary Caldwell might be used as a holding midfielder rather than in central defence. Caldwell, like Christophe Berra and Steven Naismith, has slipped out of the first team at club level recently and Strachan admitted that training highlighted varying degrees of sharpness among his players. "That is a problem. I didn't think it would be until I became an international manager. It definitely affects people, that's for sure. You can tell the people who are playing regularly and are on top of their game.

"I had a look at them this morning and thought: 'they are quite young and fresh'. It's not as powerful as the team has been before so we have to use the skills we have got. The philosophy is that we have players who can pass it. The longer you can keep it, the less chance the other team have of scoring. We have to trust ourselves."