Iceland had its chances in the first half, dominating play but failing to convert its free kicks and long passes into a goal.
World Cup debutant Iceland will try not to melt in the fierce heat of Volgograd when it takes on Nigeria after holding two-time champion Argentina to a draw at the weekend.
A draw would be enough to eliminate the Argentines but would leave Nigeria's fate hinging on the outcome of Iceland's game against Croatia.
And to add to the Everton talisman's misery, he missed a penalty in the dying embers, which would have given the Iceland team fresh impetus with 10 minutes remaining as they tried desperately to snatch a draw.
After two disappointing performances from group favorite Argentina, it looked as though Iceland's path to advancing was clear, but on Friday the tiny island nation fell to Nigeria, and now we won't know who will escape to the knockout stage until the final two matches are played on Tuesday.
"This is a must-win game for Nigeria and that makes it a little bit psychologically different, they have to win", he said. Iceland holds a slight advantage over Argentina with a -2 goal difference to Argentina's -3.
Alex Iwobi will be hoping to start again on the wing, and his trickery will be a needed if Nigeria is to break down the Iceland defence.
The result was also a boost for Lionel Messi's Argentina, who are now back in the mix in Group D.
With his double, Musa is now the highest-scoring Nigerian at the World Cup finals with four goals.
"I've always said that when everyone is rowing in the same direction then anything is possible in football", said Gunnarsson. Gernot Rohr will be hoping that his youthful squad has learnt from their opener, and taken those lessons into the game against Iceland a side who are similarly defensively robust.