The fans sipped on their cold Einstök ale, while chanting "ĺs-land!" But it was Musa who truly vindicated his manager's decisions, popping up with two brilliant goals while proving a constant menace to Iceland's usually unflappable defence.
And captain Aron Gunnarsson said it was the team's togetherness and spirit that enabled them to keep punching above their weight on the world stage, having famously knocked England out of Euro 2016.
The Nigerian team also had a stroke of luck as Iceland won a fair penalty-which was then sailed over the bar by their star player Siggurdson.
Nigeria offered nothing during a lacklustre first half but Musa turned on the style after the break, first finding the roof of the net with a brilliantly-taken half-volley before a fine individual effort doubled his side's advantage.
"I think it worked out well".
Things got even worse for Iceland, as centre-back Ragnar Sigurdsson copped a head knock during the build up to the goal, and had to receive treatment before the restart of play.
The Super Eagles, meanwhile, know that a draw against Argentina will probably be sufficient, unless Iceland beat Croatia and better Nigeria's goal difference.
The Super Eagles of Nigeria finally took flight in Russian Federation at the World Cup, and Ahmed Musa's two goals gave Nigeria a crucial win over Iceland in the group stage.
Group D is now set for a blockbuster finale on Tuesday when Iceland take on already-qualified Croatia in Rostov and Nigeria face Argentina in St. Petersburg. His two previous World Cup goals at the 2014 tournament in Brazil were in a group match against Argentina. But should Iceland fail to beat group leaders Croatia in their final match, a draw or better for Nigeria will be enough for them to progress.
Iceland is dreaming of the knockout stage and writing a new chapter in one of the most outstanding stories of worldwide football in recent years.