A win or draw at Seville's Estadio La Cartuja on Thursday, October 12, would see the Scots through to a major tournament - even a loss could do the trick if Norway fail to win in Cyprus.
It's the latest chapter in an inspirational qualifying campaign that has seen the team win five out of five games and sit atop qualifying Group A on 15 points, a run that included a memorable 2-0 win over Spain at Hampden.
But if there was any doubt of how tough a challenge they face taking on Spain in their own backyard, a glance at the match odds will provide a sobering experience.
Here are the bookies' 12 most likely results - and the odds of them happening.
5. Spain 3-1 Scotland
The top five most likely scores are completed with yet another Spain win - they are 9/1 to win 3-1. | Getty Images
6. Spain 1-1 Scotland
The first ray of hope for the Tartan Army - you can get odds of 9/1 on a 1-1 draw in Spain. | Getty Images
7. Spain 0-0 Scotland
Another drawn scoreline - this time 0-0 - is priced at 12/1. | Getty Images
8. Spain 4-0 Scotland
More bad news for Scotland - the bookies have a 4-0 win for Spain at the relatively short odds of 12/1. | Getty Images