|Scotland v Republic of Ireland|
|Venue: Celtic Park Date: 14 November Kick-off: 19:45 GMT|
|Coverage: Live on BBC Radio Scotland & online. Live text on BBC Sport website.|
The focus ahead of Scotland's meeting with the Republic of Ireland has been on nostalgia.
It seems like an old reunion when so many connected with both squads have worked together, or spent parts of their careers at Celtic. The context provides an easy narrative, but it is also a diversion: Scotland have not faced a more critical fixture under Gordon Strachan.
The Group D table has already become cluttered. Only four points separates five sides, with Gibraltar cast adrift.
The expectation was that Germany would climb free of the scramble between Scotland, the Republic, Poland and Georgia, but the World Cup winners have stumbled into a careless streak.
That will not unduly trouble Strachan, since he will assume that the Germans will eventually recover their poise, leaving the others to fight it out.
Even so, the opening games in Euro 2016 qualifying have exposed how fragile the sense of progress under Strachan can be.
There is no doubt that the team has improved, and with that a mood of optimism has grown, but in such a tight contest there is little room for error.
Scotland will feel that the performance for spells against Germany, at a time when Joachim's Loew's team was not a clinically accomplished as they were in Brazil last summer, might have merited more than a gritty 2-1 defeat.
That was emphasised when the Germans subsequently lost to Poland. Then on the same night that Scotland earned a 2-2 draw in Warsaw - and again may have felt that the performance ought to have brought more - the Republic were earning a 1-1 draw in Gelsenkirchen.
Assumptions about the group have been undone.
Scotland will always have considered it essential to defeat the Republic at home, along with Poland and Georgia, so the scope of the task on Friday night at Celtic Park hasn't changed. Defeat, though, would leave Martin O'Neill's side six points clear of Scotland, albeit with six games remaining.
How it might affect the mood around the national team would be even more considerable.
Strachan has overseen a rise in the standard of the team's play, but also the belief amongst the players and the supporters that qualification is achievable. A victory over the Republic would underline that the faith is not misplaced. More importantly, it would continue the momentum that Strachan has built.
|Scotland's remaining Euro 2016 qualifiers|
|14 November, 2014||R of Ireland (h)|
|29 March, 2015||Gibraltar (h)|
|13 June, 2015||R of Ireland (a)|
|4 September, 2015||Georgia (a)|
|7 September, 2015||Germany (h)|
|8 October, 2015||Poland (h)|
|11 October, 2015||Gibraltar (a)|
The impression of improvement is not wistful, though. Strachan has built on the foundations of the squad, working intensely on the training ground on shape and tactics, but also inside the minds of his players.
Individuals have thrived, among them players fresh to the squad like Andrew Robertson, the Hull City full-back, and Ikechi Anya, the Watford midfielder.
Scotland now have a recognisable pattern of play and a better balance between resistance at the back and creativity in attack.
There is still room for hard-headed decisions - Robertson was replaced in the starting line-up for the game against Poland by Steven Whittaker, a more experienced defender - but the evidence remains that Strachan has been delivering more coherent and more effective performances from his squad.
The team is capable of moments of attacking intent, with individuals like Steven Naismith, Anya, Shaun Maloney and James Morrison granted the freedom to play imaginatively in the final third, as long as that is accompanied by work-rate and intensity when the opposition are in possession.
The squad is imbalanced, since strong options in midfield are not replicated in central defence, yet Strachan has made partnerships work between Grant Hanley and Russell Martin, or with Gordon Greer stepping in as a replacement.
There is a shrewdness to the Scotland manager, but also a pragmatism. Public opinion once clamoured for Jordan Rhodes to be a regular in the starting line-up, but he has quietly and firmly been moved to the periphery. There has been little outcry, because the team has performed impressively in his absence.
A victory over the Republic at Celtic Park is crucial, but it is also valid to believe that it is well within the team's capabilities.
Assistant manager Mark McGhee remarked that the two squads are very similar, since many players are drawn from the same leagues. There are plenty of dependable figures in O'Neill's squad, as well as top-level experience in the likes of John O'Shea, Darron Gibson and Robbie Keane.
Yet Scotland have players operating at the top of the game in England, too, among them Naismith, Steven Fletcher, Morrison, Graham Dorrans and, slowly regaining his match sharpness, Darren Fletcher. Scotland have no cause to be anxious ahead of the game, although it is not uncommon for the national team to struggle in games that they are required, and expected, to win.
Strachan has little time for mental weaknesses. Robertson has thrived because of his attitude, his willingness to learn and to be self-assured, as much as his burgeoning ability.
The Scotland manager has predicted that the game will be full of heart, spirit, athleticism and aggression, but it is nerve and guile that will prove decisive.
Scotland have proved themselves to be resilient - in their last 12 games they have only lost three times, to Belgium, England and Germany - and as the stature and confidence of the players has grown, so too has the onus on them to produce effective displays in key games.
This is the most important fixture of Strachan's time as Scotland manager, since it will influence and shape the rest of the campaign. For all the progress seen so far, the mood of confidence and conviction will soar or collapse on the basis of 90 minutes.