The Real Oviedo player spoke of how excited Iceland players are at being paired with Argentina and of how he looks forward to taking on the Barcelona ace.
"It's a little scary to go up against Messi, given that he's the best in the world," Johannesson told Argentine radio station Super Deportivo Radio.
Indeed, right-back Johannesson has warned Messi to prepare himself for an onslaught when the two teams meet in Moscow on June 16 - if only because the Barca striker is going to bring an awful lot of souvenirs with him.
"Obviously all of our players will want Messi's shirt and I'm no exception. He'll of course give it to whoever asks him first, so I would tell Messi to prepare 23 shirts for all of those in the squad who play and also those who don't."
Speaking more generally about Iceland's chances at their first ever World Cup, the right-back exuded confidence.
"We can beat anybody and ill try to do that," he said. "What we're doing is something we've now been doing for a few years. It was seen at Euro 2016 that our success isn't a fluke."
Johannesson also explained that he has double nationality, as his father is Icelandic, while he was born in Spain.
Yet he has chosen to represent the island country.