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.
1. Spain 1-0 Scotland
The most likely result according to the bookies is a single goal win for the Spanish - priced at 5/1.
2. Spain 2-0 Scotland
The second most likely score - with odds of 9/2 - is a two goal win for the home team.
3. Spain 2-1 Scotland
A tense 2-1 win for Spain is the fourth favourite when it comes to predicting the right result. It's priced at 7/1.
4. Spain 3-0 Scotland
It may come as a surpise to Scottish fans that the bookies even see a 3-0 Spanish win more likely that a draw - never mind a Scottish win. It's the third most favoured result, priced at 13/2.