The Iceland skipper who can play either as a defensive midfielder or a central midfielder will play a pivotal role in Iceland's opening fixture against Argentina.
After Cristiano Ronaldo's heroics for Portugal last night the pressure is on Lionel Messi to deliver for Argentina.
"We've shown that if we work together as one unit, like we've been doing, then anything is achievable and it won't come as a shock", he said.
Juventus striker Higuain will be left out in favour of Aguero, who is overcoming a knee injury that kept him out of Manchester City's final games of the Premier League season. "We'll help each other and try to do it as a team".
Aguero will play in front of talisman Lionel Messi, with Angel Di Maria and Maximiliano Meza on either side of the Barcelona forward.
When asked how Iceland would handle five-time World Player of the Year Messi, Hallgrimsson cited his team's all-for-one ethos.
"Regarding Messi, I don't have a magic formula".
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Alan Dzagoev had been at the heart of things but had to go off after pulling a hamstring in the 23rd minute. I'm happy we won and happy I could help my team", said man-of-the match Cheryshev.
They may be the smallest nation to qualify for a World Cup finals, but after reaching the last eight of Euro 2016 and qualifying for Russian Federation, they are ranked 22nd in the world by FIFA. "Everyone's tried everything against him and he always manages to score", he said.
- Only Bolivia (18) scored fewer goals than Argentina (19) in the CONMEBOL qualifiers for the 2018 World Cup.
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Argentina beat Haiti 4-0 in their warm-up friendly ahead of the tournament as Messi grabbed a hat-trick, but given the standard of opposition it's hard to get carried away.
Messi is a man on a mission as he chases his first World Cup winner's medal.
Marcos Rojo and Maxi Meza were the only question marks, but have been given the nod to start at Spartak Stadium against the Euro 2016 quarter-finalists.
Friendlies against Nicaragua and Israel had to be cancelled due to safety concerns so Iceland will aim to take advantage of any rustiness in their first game at a World Cup finals.