The 31-year-old scrum-half, who quit the international game yesterday, had no hesitation in making his selection. "It was my first game as captain of Scotland, at home against England in 2008. I got the man-of-the-match award and we won."
"My clearest memory, though, is of the build-up to the game. We had gone out for the warm-up and the weather was great. Then, when we were in the tunnel waiting to go out, all you could see was the rain teeming down and, in a weird way, being Scottish, I saw that and thought: 'This is our game to lose.' "
The other moment he selects as having stood out came later that year when he became the only Scottish player to date to be nominated on the short-list for the International Rugby Board's world player of the year award.
"It was a real thrill to be sitting down for dinner with the likes of Richie McCaw, Dan Carter and Shane Williams, who won it that year. I knew I had no chance, but it was an honour to be in that company," he said.
It was far from an undue one for a player whose prolonged individual excellence probably deserved much more from his time in Test rugby, as could be said of several other Scottish players of his generation.
The harshness of the professional environment, ruthlessly exploiting every vulnerability in any team, has exposed the lack of depth of quality of Scottish rugby as never before, meaning that only once in his decade-long career – under Frank Hadden in 2006 – has Blair been part of a squad that has finished in the top half of the Six Nations Championship table.
Yet on a personal level his class was obvious from his time on the domestic club scene with Boroughmuir onwards.
That was never more obvious than when, newly turned professional, he went on his first international tour, to North America in 2002. Graeme Burns, his rival scrum-half, was captain of the Edinburgh club that Blair had just joined but there was something about the way the youngster carried himself throughout that made it seem inevitable when he was chosen to wear the No.9 jersey in both Test matches against Canada and the USA.
Thereafter, he under-studied Bryan Redpath, the squad captain, at the 2003 World Cup before Matt Williams took over as Scotland coach and, as part of his attempt to shake things up, promoted the novice professional Chris Cusiter ahead of his fellow Boroughmuir graduate, to the starting role in the Scotland team.
It speaks to Blair's attitude that his response was to play a leading role in helping Edinburgh make the long-awaited Scottish breakthrough in the Heineken Cup in which they reached that season's quarter-finals.
They remained the only team to have gone that far until – with Blair again featuring as one of only two survivors of that 2003/04 campaign to be involved – Edinburgh reached the semi-finals last year.
That period was the start of a friendly rivalry with Cusiter that has lasted to this day and perhaps reached its height when Andy Robinson, on taking over as Scotland head coach, found it so hard to choose between the two that he initially made them co-captains.
It became a three-way battle after Rory Lawson, who spent a large chunk of his career as Blair's understudy, emerged from that role by moving to Gloucester and forced his way into contention.
He, too, has gone on to captain his country, doing so during the 2011 World Cup in New Zealand. Yet, as was observed yesterday by Chris Paterson, Scotland's record cap holder and points scorer who was a near constant presence in the national squad between 1999 and 2011, Blair spent a full decade featuring in every Scotland matchday squad for which he was fit.
That bears testimony to his importance to the squad as both player and leader while part of Blair's reasoning for the timing of his departure from the international game speaks to his commitment to the cause.
He had been considering his situation since last summer, balancing his awareness that he is currently still good enough to play at Test level, with his understanding that participation in the 2015 World Cup – by which time he will be 34 – was probably beyond him.
Blair explained that he had consequently discussed all of that with Andy Robinson during the autumn, so fully understood the then national team's head coach's reasoning when he wanted to give Henry Pyrgos the chance to start against Tonga but had also promised Lawson some involvement in the series.
Pyrgos had seized his unexpected chance when he came off the bench to score a try against South Africa the week before that match, an opportunity that emerged after Blair had been immediately replaced after his pass was intercepted and led directly to the match-clinching Springbok try.
In one sense, it is slightly sad that throwing that pass was the final act of this magnificent Test career in which, as well as amassing 85 Scotland caps, he also toured South Africa with the British & Lions four years ago.
However, it is just another mark of the calibre of the man, since it would have been tempting for him to extend his career and look for what might have appeared a better way to end things.
Instead, he has shown the self-belief and awareness to realise that, far from being remembered for any one mistake, his reputation can rest on what amounts to a formidable body of work in his chosen field.