The World Cup debutants, who stunned twice champions Argentina last Saturday with a 1-1 draw, had gone into the interval feeling they were on track at 0-0, with Nigeria failing to register a single shot. Always a menacing figure down the flanks, Moses completed four dribbles, made three clearances, three blocks and completed 57 passes on a game that was completely dominated by the West-African giants.
The formation change allowed Nigeria to pack the middle of the pitch, forcing Iceland to go wide and negating the influence of Sigurdsson.
Iceland's best weapons were set play.
But Sigurdsson could not hit the target, and now Iceland know they will need to beat Croatia but progress is out of their hands. "I think Nigeria will beat Argentina, and Croatia and Nigeria will move on to the second stage", an Iceland fan said.
Fantastic, fantastic, it was a good match, we are very grateful to have won it, it is very good for Nigeria, we are all happy!
Coach Heimir Hallgrimsson said things had been going to plan with the scores 0-0 at halftime but the heat of Volgograd, with temperatures of around 30 degrees Celsius (86°F) throughout the game, sapped his team. Nigeria, with three points thanks to the win over Iceland, faces Argentina, which has a point due to its draw with Iceland last week, on Tuesday. They made the headlines two years ago when they shockingly qualified from the group stages of their first ever global tournament before beating England.
Nigeria are now on a World Cup losing streak of three games, their worst run since losing four matches between 1998 and 2002.
Rohr is hopeful his young charges - Nigeria is the youngest squad at the World Cup - will push on against Lionel Messi's Argentina.
Iceland were then handed a way back into the game from the penalty spot, after the New Zealander Matthew Conger consulted VAR to confirm the substitute Tyronne Ebuehi had brought down Alfred Finnbogason.
"We were ahead of them in our group and we've already beaten them once in Iceland, so we at least have that confidence with us when we play them", he said.
The victory put Nigeria in second place in Group D, with three points from two matches.
His words: "Since I have been in Nigeria for two years now we play Mikel in this role as an offensive midfielder".
Iceland have failed to score a goal in a match at either the European Championships or World Cup for the first time, in what was their seventh such game (five at the Euros, two at the World Cup).